TED2007
Emily Oster: Flip your thinking on AIDS in Africa
艾蜜莉·奧斯特(Emily Oster)顛覆我們對非洲愛滋病的想法
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艾蜜莉·奧斯特從經濟學角度，重新檢視非洲愛滋病的數據，有了驚人的結論：我們對愛滋病病毒在非洲的傳播認知是錯誤的。
Emily Oster - Assumption-busting economist
Emily Oster, a University of Chicago economist, uses the dismal science to rethink conventional wisdom, from her Harvard doctoral thesis that took on famed economist Amartya Sen to her recent work debunking assumptions on HIV prevalence in Africa. Full bio
Emily Oster, a University of Chicago economist, uses the dismal science to rethink conventional wisdom, from her Harvard doctoral thesis that took on famed economist Amartya Sen to her recent work debunking assumptions on HIV prevalence in Africa. Full bio
Double-click the English transcript below to play the video.
00:26
So I want to talk to you today about AIDS in sub-Saharan Africa.
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我今天要講的是撒哈拉以南非洲的愛滋病情形
00:29
And this is a pretty well-educated audience,
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各位教育程度都很高
00:31
so I imagine you all know something about AIDS.
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所以大家應該都知道愛滋病
00:34
You probably know that roughly 25 million people in Africa
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在非洲有2500萬人
00:36
are infected with the virus, that AIDS is a disease of poverty,
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感染愛滋病病毒，而且它也是窮人的疾病
00:40
and that if we can bring Africa out of poverty, we would decrease AIDS as well.
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如果能幫助非洲脫離貧窮，那愛滋病也會減少
00:44
If you know something more, you probably know that Uganda, to date,
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還有，烏干達現在是撒哈拉以南非洲地區
00:47
is the only country in sub-Saharan Africa
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唯一成功對抗這流行病
00:49
that has had success in combating the epidemic.
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的國家
00:52
Using a campaign that encouraged people to abstain, be faithful, and use condoms --
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他們宣導ABC運動：戒絕、忠貞、保險套
00:56
the ABC campaign -- they decreased their prevalence in the 1990s
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成功在1990年，減低愛滋傳播率
01:00
from about 15 percent to 6 percent over just a few years.
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幾年間，從15%降到6%
01:04
If you follow policy, you probably know that a few years ago
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如果你關心政策，你應該知道幾年前
01:07
the president pledged 15 billion dollars to fight the epidemic over five years,
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總統投入15億美元，對抗愛滋病
01:11
and a lot of that money is going to go to programs that try to replicate Uganda
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大部分的資金，都投入類似烏干達的計畫
01:14
and use behavior change to encourage people and decrease the epidemic.
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利用行為改變，來鼓勵人們，以減低傳染
01:20
So today I'm going to talk about some things
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所以我今天要談一些
01:22
that you might not know about the epidemic,
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關於愛滋，你們所不知道的事
01:24
and I'm actually also going to challenge
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再來我要挑戰一些
01:26
some of these things that you think that you do know.
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你們已知的事
01:28
To do that I'm going to talk about my research
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我先談我身為經濟學家
01:31
as an economist on the epidemic.
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對於愛滋病所做的研究
01:33
And I'm not really going to talk much about the economy.
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我不會談太多經濟的東西
01:35
I'm not going to tell you about exports and prices.
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也不會講進出口價格
01:38
But I'm going to use tools and ideas that are familiar to economists
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但我要用一些經濟學家常用的方法
01:42
to think about a problem that's more traditionally
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來解釋流行病學、公共衛生
01:44
part of public health and epidemiology.
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衍生出的問題
01:46
And I think in that sense, this fits really nicely with this lateral thinking idea.
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這樣很符合橫向思維的概念
01:50
Here I'm really using the tools of one academic discipline
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運用一種學術領域的工具
01:53
to think about problems of another.
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來解決其他領域的問題
01:55
So we think, first and foremost, AIDS is a policy issue.
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首先，愛滋病跟政策有關
01:58
And probably for most people in this room, that's how you think about it.
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可能在座大部分的人，也是這麼認為
02:01
But this talk is going to be about understanding facts about the epidemic.
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但我要講的是，關於理解疫情傳播的事實
02:05
It's going to be about thinking about how it evolves, and how people respond to it.
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關於思考它的形成原因，人們的反應
02:08
I think it may seem like I'm ignoring the policy stuff,
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看來我可能會忽略政策之類的東西
02:11
which is really the most important,
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雖然政策是最重要的
02:13
but I'm hoping that at the end of this talk you will conclude
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但演講結束你會明白
02:15
that we actually cannot develop effective policy
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除非了解疾病的傳播
02:17
unless we really understand how the epidemic works.
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我們是無法訂定有效政策的
02:20
And the first thing that I want to talk about,
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我想講的第一點
02:22
the first thing I think we need to understand is:
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我們必須理解的第一點是
02:24
how do people respond to the epidemic?
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人們對於愛滋病的反應是什麼？
02:26
So AIDS is a sexually transmitted infection, and it kills you.
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愛滋病是性傳播疾病，會致死
02:30
So this means that in a place with a lot of AIDS,
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所以愛滋病盛行的地方
02:32
there's a really significant cost of sex.
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性行為的代價也高
02:34
If you're an uninfected man living in Botswana, where the HIV rate is 30 percent,
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波紮那的病毒感染率30%，如果你是個健康的男人
02:38
if you have one more partner this year -- a long-term partner, girlfriend, mistress --
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你今年多了一個性伴侶－長期的、女友、情婦也好
02:42
your chance of dying in 10 years increases by three percentage points.
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你十年內死亡率會提高三個百分點
02:46
That is a huge effect.
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這是很驚人的
02:48
And so I think that we really feel like then people should have less sex.
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所以我們會覺得，人們真的要減少性行為
02:51
And in fact among gay men in the US
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事實上，美國的同性戀中
02:53
we did see that kind of change in the 1980s.
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在1980年代，我們確實看到這種改變
02:55
So if we look in this particularly high-risk sample, they're being asked,
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仔細觀察高危險群，當他們被問到：
02:59
"Did you have more than one unprotected sexual partner in the last two months?"
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「過去的兩個月內，你是否有一個以上，未採取保護措施的性伴侶？」
03:02
Over a period from '84 to '88, that share drops from about 85 percent to 55 percent.
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數據顯示，從84到88年，比例從85%下降到55%
03:08
It's a huge change in a very short period of time.
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這麼短時間內，這是很大的改變
03:10
We didn't see anything like that in Africa.
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在非洲我們從未看到這樣的改變
03:12
So we don't have quite as good data, but you can see here
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我們沒有足夠的數據，但你可以看到
03:15
the share of single men having pre-marital sex,
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這是單身男人婚前性行為
03:17
or married men having extra-marital sex,
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或已婚男人的婚外性行為的數據比例
03:19
and how that changes from the early '90s to late '90s,
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從90年代初期到末期的改變
03:22
and late '90s to early 2000s. The epidemic is getting worse.
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以及90年末到2000年初期的改變，疫情變嚴重了
03:25
People are learning more things about it.
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人們對疾病的瞭解更多
03:27
We see almost no change in sexual behavior.
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但性行為上卻幾乎沒有變化
03:29
These are just tiny decreases -- two percentage points -- not significant.
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只有降低極少的2%而已
03:33
This seems puzzling. But I'm going to argue that you shouldn't be surprised by this,
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看來很怪，但你不應該對此感到吃驚
03:37
and that to understand this you need to think about health
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想要理解原因，你要用經濟學家的思維
03:40
the way than an economist does -- as an investment.
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來思考健康議題，用投資的概念
03:43
So if you're a software engineer and you're trying to think about
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如果你是個軟體設計師，當你在想
03:46
whether to add some new functionality to your program,
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是否要在你的設計裡，加一些新的功能時
03:49
it's important to think about how much it costs.
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成本是必須考慮的
03:51
It's also important to think about what the benefit is.
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收益也是必須考慮的
03:53
And one part of that benefit is how much longer
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考慮收益的其中一個方法就是
03:55
you think this program is going to be active.
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你的軟體離推出還有多久
03:57
If version 10 is coming out next week,
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如果第十版下週推出
03:59
there's no point in adding more functionality into version nine.
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那就沒必要更新第九版
04:02
But your health decisions are the same.
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而健康也是如此
04:04
Every time you have a carrot instead of a cookie,
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每次放棄餅乾而去吃胡蘿蔔時
04:06
every time you go to the gym instead of going to the movies,
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每次去健身房而不是看電影時
04:09
that's a costly investment in your health.
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就是你對健康極大的投資
04:11
But how much you want to invest is going to depend
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但你要投資多少
04:13
on how much longer you expect to live in the future,
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跟你能活多久有關
04:15
even if you don't make those investments.
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有沒有投資都一樣
04:17
AIDS is the same kind of thing. It's costly to avoid AIDS.
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愛滋病也是如此，防疫愛滋也是昂貴的
04:20
People really like to have sex.
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大家都喜歡做愛
04:23
But, you know, it has a benefit in terms of future longevity.
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以未來長壽來講，它確實有好處
04:29
But life expectancy in Africa, even without AIDS, is really, really low:
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但在非洲，即使沒有愛滋病，平均壽命還是很低
04:33
40 or 50 years in a lot of places.
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大部分地方是40到50歲
04:36
I think it's possible, if we think about that intuition, and think about that fact,
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這樣可以馬上理解
04:40
that maybe that explains some of this low behavior change.
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低行為改變的原因了
04:43
But we really need to test that.
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但仍需要證實
04:45
And a great way to test that is to look across areas in Africa and see:
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證實的方法就是，看非洲地區
04:48
do people with more life expectancy change their sexual behavior more?
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平均壽命高的地方，性行為是否有較大的改變？
04:52
And the way that I'm going to do that is,
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我的作法是
04:54
I'm going to look across areas with different levels of malaria.
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調查不同程度的瘧疾地區
04:57
So malaria is a disease that kills you.
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瘧疾也是會致命的疾病
05:00
It's a disease that kills a lot of adults in Africa, in addition to a lot of children.
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在非洲，無數的大人、小孩因此死亡
05:03
And so people who live in areas with a lot of malaria
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所以住在瘧疾病率高地區的人
05:06
are going to have lower life expectancy than people who live in areas with limited malaria.
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平均壽命低於瘧疾不嚴重地區的人
05:10
So one way to test to see whether we can explain
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所以我們研究
05:12
some of this behavior change by differences in life expectancy
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壽命是否會影響行為改變的方法
05:15
is to look and see is there more behavior change
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就是觀察瘧疾病率低的地區
05:18
in areas where there's less malaria.
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是否有較大的行為改變
05:20
So that's what this figure shows you.
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這是我們的數據
05:22
This shows you -- in areas with low malaria, medium malaria, high malaria --
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分別是低、中、高程度瘧疾病率的地區
05:26
what happens to the number of sexual partners as you increase HIV prevalence.
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當愛滋病毒傳播增加時，性伴侶的數量情形
05:30
If you look at the blue line,
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看這條藍線
05:32
the areas with low levels of malaria, you can see in those areas,
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在這些瘧疾較少的地區
05:35
actually, the number of sexual partners is decreasing a lot
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當愛滋病毒傳播率提高時
05:38
as HIV prevalence goes up.
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性伴侶數量是大量減少的
05:40
Areas with medium levels of malaria it decreases some --
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中程度瘧疾地區
05:42
it doesn't decrease as much. And areas with high levels of malaria --
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雖然也有減少但不明顯，高程度瘧疾地區
05:45
actually, it's increasing a little bit, although that's not significant.
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反而增加，雖然數目不大
05:50
This is not just through malaria.
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還不只是瘧疾
05:52
Young women who live in areas with high maternal mortality
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高產婦死亡率地區的年輕婦女
05:55
change their behavior less in response to HIV
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為了防止愛滋病毒所做的行為改變
05:58
than young women who live in areas with low maternal mortality.
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比低產婦死亡率地區的年輕婦女還少
06:01
There's another risk, and they respond less to this existing risk.
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因為有其他風險，所以他們對於已知風險的反應不大
06:06
So by itself, I think this tells a lot about how people behave.
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這解釋了許多人類的行為
06:09
It tells us something about why we see limited behavior change in Africa.
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像是為什麼非洲的行為改變有限
06:12
But it also tells us something about policy.
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但還有政策的成效
06:14
Even if you only cared about AIDS in Africa,
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即使你只關心在非洲的愛滋病情況
06:17
it might still be a good idea to invest in malaria,
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一起投資改善瘧疾、
06:20
in combating poor indoor air quality,
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室內的空氣品質、
06:22
in improving maternal mortality rates.
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降低產婦死亡率也是很重要的
06:24
Because if you improve those things,
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因為改變了這些
06:26
then people are going to have an incentive to avoid AIDS on their own.
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人們就會自覺性的防治愛滋病
06:30
But it also tells us something about one of these facts that we talked about before.
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這也證實我們先前所提的
06:34
Education campaigns, like the one that the president is focusing on in his funding,
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總統一直投入資金的教育活動
06:38
may not be enough, at least not alone.
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是不夠的
06:40
If people have no incentive to avoid AIDS on their own,
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如果他們沒有防治愛滋病的自覺
06:42
even if they know everything about the disease,
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就算他們了解這疾病
06:44
they still may not change their behavior.
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還是不會改變他們的行為
06:46
So the other thing that I think we learn here is that AIDS is not going to fix itself.
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我們知道愛滋不會自癒
06:49
People aren't changing their behavior enough
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就算人們改變行為
06:51
to decrease the growth in the epidemic.
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傳染率降幅也不大
06:54
So we're going to need to think about policy
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我們要重新考慮政策
06:56
and what kind of policies might be effective.
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找出更有效的政策
06:58
And a great way to learn about policy is to look at what worked in the past.
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了解政策的方法，可以從過去的情形來看
07:01
The reason that we know that the ABC campaign
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我們知道，ABC運動
07:03
was effective in Uganda is we have good data on prevalence over time.
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在烏干達這麼有效的原因，是因為當時有數據
07:06
In Uganda we see the prevalence went down.
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可以看出傳染率下降
07:08
We know they had this campaign. That's how we learn about what works.
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我們知道是ABC運動的關係，所以做出此結論
07:11
It's not the only place we had any interventions.
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但不只有烏干達有活動
07:13
Other places have tried things, so why don't we look at those places
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其他地方也有政策，那我們怎麼
07:17
and see what happened to their prevalence?
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不看看那些地方的情形呢？
07:20
Unfortunately, there's almost no good data
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不幸的，我們並沒有2003年
07:22
on HIV prevalence in the general population in Africa until about 2003.
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非洲普遍人口的愛滋病毒感染情形
07:27
So if I asked you, "Why don't you go and find me
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所以如果要找布基那法索國
07:29
the prevalence in Burkina Faso in 1991?"
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1991年傳染率數據
07:32
You get on Google, you Google, and you find,
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用Google查一下，你會發現
07:35
actually the only people tested in Burkina Faso in 1991
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1991年布基那法索國受測者
07:38
are STD patients and pregnant women,
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都是性病患者和懷孕婦女
07:40
which is not a terribly representative group of people.
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這群受測對象還可以
07:42
Then if you poked a little more, you looked a little more at what was going on,
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但如果深入調查，你會發現
07:45
you'd find that actually that was a pretty good year,
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當年的結果是不錯的
07:48
because in some years the only people tested are IV drug users.
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其他年的受測對象都是靜脈藥癮者
07:51
But even worse -- some years it's only IV drug users,
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更糟的是，有些年是測靜脈藥癮者
07:53
some years it's only pregnant women.
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有些年只有測懷孕婦女
07:55
We have no way to figure out what happened over time.
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根本無法得知當時情形
07:57
We have no consistent testing.
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也沒有持續抽樣檢察
07:59
Now in the last few years, we actually have done some good testing.
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但幾年後，我們確實做了一些抽檢
08:04
In Kenya, in Zambia, and a bunch of countries,
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在肯亞、尚比亞和一些國家
08:07
there's been testing in random samples of the population.
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都有一些隨機抽樣
08:10
But this leaves us with a big gap in our knowledge.
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但數據上還是留了很大一片空白
08:13
So I can tell you what the prevalence was in Kenya in 2003,
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我能告訴你，肯亞2003年的感染情況
08:16
but I can't tell you anything about 1993 or 1983.
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但我無法提供1993年或1983年的情況
08:19
So this is a problem for policy. It was a problem for my research.
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這是政策的問題，也是我研究遇到的問題
08:23
And I started thinking about how else might we figure out
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所以我開始想其他可能的辦法
08:27
what the prevalence of HIV was in Africa in the past.
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以獲得非洲過去的愛滋病毒傳染率數據
08:29
And I think that the answer is, we can look at mortality data,
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我想到的方法是，利用死亡率數據
08:33
and we can use mortality data to figure out what the prevalence was in the past.
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來算出過去的愛滋病毒傳染率
08:37
To do this, we're going to have to rely on the fact
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所以我們只能用愛滋病
08:39
that AIDS is a very specific kind of disease.
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有個獨特性－
08:41
It kills people in the prime of their lives.
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會在人類黃金時期致死－這點
08:43
Not a lot of other diseases have that profile. And you can see here --
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其他疾病都沒有這個特點，所以可以看到：
08:46
this is a graph of death rates by age in Botswana and Egypt.
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這是波紮那和埃及的死亡率，以年齡劃分
08:50
Botswana is a place with a lot of AIDS,
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波紮那是愛滋盛行的地區
08:52
Egypt is a place without a lot of AIDS.
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埃及是愛滋不盛行的地區
08:54
And you see they have pretty similar death rates among young kids and old people.
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他們的兒童、老人死亡率相似
08:57
That suggests it's pretty similar levels of development.
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表示他們有相似的發展水準
09:00
But in this middle region, between 20 and 45,
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但在20到45歲間的死亡率
09:03
the death rates in Botswana are much, much, much higher than in Egypt.
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波紮那死亡率高出埃及很多
09:07
But since there are very few other diseases that kill people,
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但其他會致死的並不多
09:11
we can really attribute that mortality to HIV.
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我們能將死亡率歸因為愛滋
09:14
But because people who died this year of AIDS got it a few years ago,
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但愛滋感染到死亡的期間很長
09:18
we can use this data on mortality to figure out what HIV prevalence was in the past.
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我們就用死亡率推回幾年前愛滋傳染率
09:23
So it turns out, if you use this technique,
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所以，用這方法
09:25
actually your estimates of prevalence are very close
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我們能估算，受測結果
09:27
to what we get from testing random samples in the population,
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與估計的愛滋傳染率是很接近的
09:30
but they're very, very different than what UNAIDS tells us the prevalences are.
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但卻與聯合國愛滋病規劃署(UNAIDS)提供的數據大不相同
09:35
So this is a graph of prevalence estimated by UNAIDS,
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這是UNAIDS的傳染率統計
09:38
and prevalence based on the mortality data
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以及1990年後期非洲九國
09:40
for the years in the late 1990s in nine countries in Africa.
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的死亡率數據
09:44
You can see, almost without exception,
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可以看出，幾乎沒有例外
09:46
the UNAIDS estimates are much higher than the mortality-based estimates.
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UNAIDS的估計高出死亡率估計許多
09:50
UNAIDS tell us that the HIV rate in Zambia is 20 percent,
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UNAIDS說尚比亞愛滋傳播率20%
09:54
and mortality estimates suggest it's only about 5 percent.
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但死亡率估計只有5%
09:58
And these are not trivial differences in mortality rates.
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這種差距是很大的
10:01
So this is another way to see this.
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從另一方向來看
10:03
You can see that for the prevalence to be as high as UNAIDS says,
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如果傳播率有UNAIDS說的這麼高
10:05
we have to really see 60 deaths per 10,000
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那死亡率應為1萬名中有60人死亡
10:07
rather than 20 deaths per 10,000 in this age group.
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而不是1萬名有20人死亡的比例
10:11
I'm going to talk a little bit in a minute
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我想用一分鐘稍微來談
10:13
about how we can use this kind of information to learn something
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我們要怎麼用這種知識
10:16
that's going to help us think about the world.
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來解決現有的問題
10:18
But this also tells us that one of these facts
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我也會談到，演講開始時
10:20
that I mentioned in the beginning may not be quite right.
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提到的某一點，其實是錯誤的
10:23
If you think that 25 million people are infected,
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如果250萬人感染，
10:25
if you think that the UNAIDS numbers are much too high,
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或者UNAIDS估計太高，
10:28
maybe that's more like 10 or 15 million.
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那說... 100-150萬好了
10:30
It doesn't mean that AIDS isn't a problem. It's a gigantic problem.
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這樣估計不表示愛滋不是問題，愛滋很嚴重
10:34
But it does suggest that that number might be a little big.
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但這表示數字有點灌水了
10:38
What I really want to do, is I want to use this new data
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我希望做的是，利用這新數據
10:40
to try to figure out what makes the HIV epidemic grow faster or slower.
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來解答愛滋病毒傳播快慢的原因
10:44
And I said in the beginning, I wasn't going to tell you about exports.
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如我一開始說的，我不談進出口
10:47
When I started working on these projects,
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但我做了一些計畫
10:49
I was not thinking at all about economics,
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雖然不是以經濟為出發點
10:51
but eventually it kind of sucks you back in.
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但最後總會回到經濟來
10:54
So I am going to talk about exports and prices.
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我要說的是進出口價格
10:57
And I want to talk about the relationship between economic activity,
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各國的經濟活動、出口量以及
11:00
in particular export volume, and HIV infections.
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愛滋病毒感染的關係
11:04
So obviously, as an economist, I'm deeply familiar
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身為經濟學家，我明白
11:08
with the fact that development, that openness to trade,
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對於發展中國家來說
11:10
is really good for developing countries.
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出口發展、自由是很重要的
11:12
It's good for improving people's lives.
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可以促進生活品質
11:15
But openness and inter-connectedness, it comes with a cost
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但以疾病角度來說
11:17
when we think about disease. I don't think this should be a surprise.
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這種自由與交流是有代價的
11:20
On Wednesday, I learned from Laurie Garrett
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星期三，蓋瑞特(全球衛生研究員)說
11:22
that I'm definitely going to get the bird flu,
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我一定會得禽流感
11:24
and I wouldn't be at all worried about that
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但要是我們和亞洲沒有接觸
11:27
if we never had any contact with Asia.
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根本不必擔心
11:30
And HIV is actually particularly closely linked to transit.
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而愛滋病毒與運輸是緊密相連的
11:34
The epidemic was introduced to the US
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愛滋當時傳到美國
11:36
by actually one male steward on an airline flight,
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其實是因為飛機上一名男空服員
11:40
who got the disease in Africa and brought it back.
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從非洲將病毒帶回來
11:42
And that was the genesis of the entire epidemic in the US.
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也是美國愛滋病的開端
11:45
In Africa, epidemiologists have noted for a long time
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在非洲，病理學家很早之前就發現
11:49
that truck drivers and migrants are more likely to be infected than other people.
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移民者、卡車司機的感染率高於其他人
11:53
Areas with a lot of economic activity --
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如果該地有很多經濟活動、
11:55
with a lot of roads, with a lot of urbanization --
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很多道路、非常都市化
11:58
those areas have higher prevalence than others.
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那麼傳染率則較普及
12:00
But that actually doesn't mean at all
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但也不代表
12:02
that if we gave people more exports, more trade, that that would increase prevalence.
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如果有更多交易、出口，就會增加感染率
12:06
By using this new data, using this information about prevalence over time,
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利用這個傳染率的數據
12:10
we can actually test that. And so it seems to be --
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我們可以測試看看
12:14
fortunately, I think -- it seems to be the case
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結果證明是對的
12:16
that these things are positively related.
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這些東西是相互關聯的
12:18
More exports means more AIDS. And that effect is really big.
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越多出口、越多愛滋，影響極大
12:22
So the data that I have suggests that if you double export volume,
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數據顯示，如果出口數加一倍
12:26
it will lead to a quadrupling of new HIV infections.
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愛滋感染率會增加四倍
12:31
So this has important implications both for forecasting and for policy.
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因此在預測、政策上都要將此納入考量
12:34
From a forecasting perspective, if we know where trade is likely to change,
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從預測的角度來看，如果我們知道交易會改變
12:38
for example, because of the African Growth and Opportunities Act
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例如，因為「非洲成長及機會法案」
12:41
or other policies that encourage trade,
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或其他鼓勵交易的法案
12:43
we can actually think about which areas are likely to be heavily infected with HIV.
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我們可以知道這些地方感染率會提高
12:48
And we can go and we can try to have pre-emptive preventive measures there.
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那就可以先發製人，做出因應措施
12:54
Likewise, as we're developing policies to try to encourage exports,
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相同的，現在許多政策都鼓勵出口
12:57
if we know there's this externality --
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如果我們知道會有外部效應－
12:59
this extra thing that's going to happen as we increase exports --
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增加出口連帶其他事情的發生
13:01
we can think about what the right kinds of policies are.
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即可想出正確的因應政策
13:04
But it also tells us something about one of these things that we think that we know.
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有些事我們早已清楚
13:07
Even though it is the case that poverty is linked to AIDS,
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即使我們知道愛滋與貧窮習習相關
13:10
in the sense that Africa is poor and they have a lot of AIDS,
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非洲窮、愛滋多
13:13
it's not necessarily the case that improving poverty -- at least in the short run,
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短期來說，不表示改善經濟
13:17
that improving exports and improving development --
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改善出口、改善當地發展
13:19
it's not necessarily the case that that's going to lead
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就能有效的
13:21
to a decline in HIV prevalence.
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降低愛滋病毒盛行率
13:24
So throughout this talk I've mentioned a few times
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剛剛我重複提了
13:26
the special case of Uganda, and the fact that
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烏干達成功的案例
13:28
it's the only country in sub-Saharan Africa with successful prevention.
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它是撒哈拉以南非洲唯一成功預防傳染的國家
13:32
It's been widely heralded.
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結果大家都開心
13:34
It's been replicated in Kenya, and Tanzania, and South Africa and many other places.
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相同政策也在肯亞、坦尚尼亞、南非等國實施
13:40
But now I want to actually also question that.
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但我懷疑它的成效
13:44
Because it is true that there was a decline in prevalence
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因為1990年代，烏干達愛滋傳播率降低
13:47
in Uganda in the 1990s. It's true that they had an education campaign.
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一半是因為有教育性的活動
13:51
But there was actually something else that happened in Uganda in this period.
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但事實上，烏干達當時發生了一件事
13:57
There was a big decline in coffee prices.
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就是咖啡價格降低
13:59
Coffee is Uganda's major export.
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烏干達主要出口是咖啡
14:01
Their exports went down a lot in the early 1990s -- and actually that decline lines up
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1990年代早期，出口是下降的，可以看出
14:06
really, really closely with this decline in new HIV infections.
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下降幅度與愛滋病毒感染幅度極為相同
14:10
So you can see that both of these series --
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可以從圖上明顯看出
14:13
the black line is export value, the red line is new HIV infections --
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黑線是出口數，紅線是愛滋病毒感染率
14:16
you can see they're both increasing.
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兩個都增加
14:18
Starting about 1987 they're both going down a lot.
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從1987年開始，大幅下滑
14:20
And then actually they track each other
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最後幾年
14:22
a little bit on the increase later in the decade.
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兩個數據又同時上升
14:24
So if you combine the intuition in this figure
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所以用你的直覺以及
14:26
with some of the data that I talked about before,
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利用我剛剛的數據可以看出
14:29
it suggests that somewhere between 25 percent and 50 percent
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烏干達傳染率的下降
14:33
of the decline in prevalence in Uganda
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有25%到50%
14:35
actually would have happened even without any education campaign.
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就算沒有教育活動也會減少
14:39
But that's enormously important for policy.
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這對於後來政策制定很重要
14:41
We're spending so much money to try to replicate this campaign.
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我們花了這麼多錢投入ABC運動
14:43
And if it was only 50 percent as effective as we think that it was,
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但只有我們預期一半的效果
14:46
then there are all sorts of other things
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所以或許我們應該
14:48
maybe we should be spending our money on instead.
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想想更多錢應該怎麼花的方法
14:50
Trying to change transmission rates by treating other sexually transmitted diseases.
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像是治療其他性傳染疾病還控制傳染率
14:54
Trying to change them by engaging in male circumcision.
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像是鼓勵男性割包皮
14:56
There are tons of other things that we should think about doing.
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還有更多的事可以做
14:58
And maybe this tells us that we should be thinking more about those things.
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我想說的是，希望大家能想些其他能做的事
15:02
I hope that in the last 16 minutes I've told you something that you didn't know about AIDS,
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我希望剛剛16分鐘內，我分享了你們所不知道的事
15:07
and I hope that I've gotten you questioning a little bit
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我希望各位能深入思考
15:09
some of the things that you did know.
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那些你們已知的事
15:11
And I hope that I've convinced you maybe
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我希望我成功說服你們
15:13
that it's important to understand things about the epidemic
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思考政策時
15:15
in order to think about policy.
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了解疾病是很重要的
15:18
But more than anything, you know, I'm an academic.
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但是，我是一個學者
15:20
And when I leave here, I'm going to go back
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當演講結束，我會回到
15:22
and sit in my tiny office, and my computer, and my data.
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我的小辦公室，對著我的電腦、數據
15:25
And the thing that's most exciting about that
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而我最興奮的事
15:27
is every time I think about research, there are more questions.
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我每次想到研究，我就會有更多的問題
15:30
There are more things that I think that I want to do.
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我想做的還有很多
15:32
And what's really, really great about being here
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能來這裡真的很棒
15:34
is I'm sure that the questions that you guys have
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我相信你們所思考的問題
15:36
are very, very different than the questions that I think up myself.
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都和我所想出的問題截然不同
15:39
And I can't wait to hear about what they are.
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而我非常期待你們想出的問題
15:41
So thank you very much.
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謝謝大家
ABOUT THE SPEAKER
Emily Oster - Assumption-busting economistEmily Oster, a University of Chicago economist, uses the dismal science to rethink conventional wisdom, from her Harvard doctoral thesis that took on famed economist Amartya Sen to her recent work debunking assumptions on HIV prevalence in Africa.
Why you should listen
Emily Oster, an Assistant Professor of Economics at the University of Chicago, has a history of rethinking conventional wisdom.
Her Harvard doctoral thesis took on famed economist Amartya Sen and his claim that 100 million women were statistically missing from the developing world. He blamed misogynist medical care and outright sex-selective abortion for the gap, but Oster pointed to data indicating that in countries where Hepetitis B infections were higher, more boys were born. Through her unorthodox analysis of medical data, she accounted for 50% of the missing girls. Three years later, she would publish another paper amending her findings, stating that, after further study, the relationship between Hepetitis B and missing women was not apparent. This concession, along with her audacity to challenge economic assumptions and her dozens of other influential papers, has earned her the respect of the global academic community.
She's also investigated the role of bad weather in the rise in witchcraft trials in Medieval Europe and what drives people to play the Powerball lottery. Her latest target: busting assumptions on HIV in Africa.
And she's an advice columnist too >>
Emily Oster | Speaker | TED.com