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TED2007

Emily Oster: Flip your thinking on AIDS in Africa

エミリー・オスターがアフリカのAIDSについて私たちの考えを変える

March 3, 2007

エミリー・オスターがアフリカでのAIDSの統計を経済的観点から見直し、おどろくべき結論に達します。アフリカ大陸でのエイズについて、私たちが知っているすべての事は間違っていると言うのです。

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

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Double-click the English subtitles below to play the video.
So I want to talk to you today about AIDS in sub-Saharan Africa.
今日はサブサハラアフリカでのAIDSについてお話します
00:26
And this is a pretty well-educated audience,
みなさん教養がありそうですので
00:29
so I imagine you all know something about AIDS.
もうAIDSについて少しは知っていますよね
00:31
You probably know that roughly 25 million people in Africa
アフリカでは2500万人が
00:34
are infected with the virus, that AIDS is a disease of poverty,
感染していて 貧困の病とも言われているAIDSは
00:36
and that if we can bring Africa out of poverty, we would decrease AIDS as well.
もしアフリカが貧困から脱却すれば
減少するだろうこともご存知でしょう
00:40
If you know something more, you probably know that Uganda, to date,
現在ウガンダが サブサハラアフリカで唯一
00:44
is the only country in sub-Saharan Africa
病との闘いに成功している国である事を
00:47
that has had success in combating the epidemic.
知っている方もいらっしゃるでしょう
00:49
Using a campaign that encouraged people to abstain, be faithful, and use condoms --
禁酒 誠実 コンドーム使用を推進する
00:52
the ABC campaign -- they decreased their prevalence in the 1990s
ABCキャンペーンで 1990年代のうちに有病率を
00:56
from about 15 percent to 6 percent over just a few years.
数年間で15%から6%にまで下げたのです
01:00
If you follow policy, you probably know that a few years ago
政策に詳しい方は 数年前に 大統領が
01:04
the president pledged 15 billion dollars to fight the epidemic over five years,
病に打ち勝つため5年にわたって150億ドルをかけると公約し
01:07
and a lot of that money is going to go to programs that try to replicate Uganda
多くのお金がウガンダを模倣したプログラムや
01:11
and use behavior change to encourage people and decrease the epidemic.
感染を減らすための行動変化の推進に
使われたことも知っているでしょう
01:14
So today I'm going to talk about some things
なので 今日はこの流行病について
01:20
that you might not know about the epidemic,
みなさんが知らないことをお話しします
01:22
and I'm actually also going to challenge
そして みなさんが事実と思っている事を
01:24
some of these things that you think that you do know.
少し くつがえしてみます
01:26
To do that I'm going to talk about my research
まず 私が経済学者として研究した
01:28
as an economist on the epidemic.
この流行病について話しますね
01:31
And I'm not really going to talk much about the economy.
しかし 輸出や価格などの経済については
01:33
I'm not going to tell you about exports and prices.
あまり話しません
01:35
But I'm going to use tools and ideas that are familiar to economists
でも経済学者としてのアイデアや道具を使って
01:38
to think about a problem that's more traditionally
本来なら 公衆衛生や伝染病学の
01:42
part of public health and epidemiology.
問題である事を話していきます
01:44
And I think in that sense, this fits really nicely with this lateral thinking idea.
これがまさに水平思考というものです
01:46
Here I'm really using the tools of one academic discipline
ここでは学問的な方法で
01:50
to think about problems of another.
問題について考えてみましょう
01:53
So we think, first and foremost, AIDS is a policy issue.
まず最初に 大切なのはAIDSは政策の問題なのです
01:55
And probably for most people in this room, that's how you think about it.
きっとこの部屋のみなさんもそう思っているでしょう
01:58
But this talk is going to be about understanding facts about the epidemic.
ただし 私がお話しするのは病についての事実と
02:01
It's going to be about thinking about how it evolves, and how people respond to it.
病がどう展開するか そしてそれに対する人々の反応です
02:05
I think it may seem like I'm ignoring the policy stuff,
政策のことを無視しているように聞こえるかもしれません
02:08
which is really the most important,
もちろんそれは一番大切ですが
02:11
but I'm hoping that at the end of this talk you will conclude
このスピーチで
02:13
that we actually cannot develop effective policy
効果的な政策を立案するには 流行病の
02:15
unless we really understand how the epidemic works.
仕組みを理解するのが必要不可欠だと知ってほしいのです
02:17
And the first thing that I want to talk about,
今からお話するのは
02:20
the first thing I think we need to understand is:
一番最初に理解しなければいけない事
02:22
how do people respond to the epidemic?
人々はどのように流行病に反応するのかです
02:24
So AIDS is a sexually transmitted infection, and it kills you.
AIDSは死をもたらす性行為感染症です
02:26
So this means that in a place with a lot of AIDS,
これは AIDSが充満している場所では
02:30
there's a really significant cost of sex.
性交渉に重大なリスクが伴うという事です
02:32
If you're an uninfected man living in Botswana, where the HIV rate is 30 percent,
HIV未感染の男性が 感染率30%のボツワナに住んでいて
02:34
if you have one more partner this year -- a long-term partner, girlfriend, mistress --
1年に1人以上の長期 彼女 愛人などのパートナーができると
02:38
your chance of dying in 10 years increases by three percentage points.
10年以内に死ぬ確率が3%増えるのです
02:42
That is a huge effect.
これは大きな影響です
02:46
And so I think that we really feel like then people should have less sex.
それなら あまり性交渉しないほうがいいように思いますよね
02:48
And in fact among gay men in the US
1980年代のアメリカでゲイの人達に
02:51
we did see that kind of change in the 1980s.
そのような挙動が実際に見られました
02:53
So if we look in this particularly high-risk sample, they're being asked,
この高リスクな例をとって 次の質問をしてみます
02:55
"Did you have more than one unprotected sexual partner in the last two months?"
「過去2ヶ月間で1人以上と安全でない性的関係を持ったか?」
02:59
Over a period from '84 to '88, that share drops from about 85 percent to 55 percent.
84年から88年の間に「はい」と答える人は85%から55%に下がりました
03:02
It's a huge change in a very short period of time.
短期間ですごい変化ですよね
03:08
We didn't see anything like that in Africa.
アフリカではそのような事はありませんでした
03:10
So we don't have quite as good data, but you can see here
いいデータがないのですが これを見てください
03:12
the share of single men having pre-marital sex,
単身男性の婚前性交 および
03:15
or married men having extra-marital sex,
既婚男性の婚外性交をする割合の
03:17
and how that changes from the early '90s to late '90s,
90年代前半から後半にかけてと 90年代後半から
03:19
and late '90s to early 2000s. The epidemic is getting worse.
2000年代にかけての変化です 流行病は悪化しているのです
03:22
People are learning more things about it.
人々は多くを学んでいるのはずなのに
03:25
We see almost no change in sexual behavior.
性行動での変化がほとんど見られないのです
03:27
These are just tiny decreases -- two percentage points -- not significant.
2%という 小さな減少は見られますが 大した事ありません
03:29
This seems puzzling. But I'm going to argue that you shouldn't be surprised by this,
それは不思議ですが 驚くような事ではありません
03:33
and that to understand this you need to think about health
それを理解するためには 健康の事を
03:37
the way than an economist does -- as an investment.
経済学者のように投資だと考える必要があります
03:40
So if you're a software engineer and you're trying to think about
もしあなたがソフトウェア技術者で 新しい機能を
03:43
whether to add some new functionality to your program,
プログラムに追加すべきか考えるときに
03:46
it's important to think about how much it costs.
費用を考えなければいけません
03:49
It's also important to think about what the benefit is.
その利益を考えるのも大切ですよね
03:51
And one part of that benefit is how much longer
利益の中にはそのプログラムが
03:53
you think this program is going to be active.
どの程度の期間 使用されるかも含まれます
03:55
If version 10 is coming out next week,
もしバージョン10が来週発売なら
03:57
there's no point in adding more functionality into version nine.
新機能をバージョン9に追加しても仕方ないですよね
03:59
But your health decisions are the same.
健康に関しても同じことです
04:02
Every time you have a carrot instead of a cookie,
クッキーのかわりににんじんを食べたり
04:04
every time you go to the gym instead of going to the movies,
映画のかわりにスポーツクラブへ行ったりすることは
04:06
that's a costly investment in your health.
健康のために投資しているという事です
04:09
But how much you want to invest is going to depend
でもどれだけ投資したいのかは これから先
04:11
on how much longer you expect to live in the future,
どれ位 生きる見込みがあるのかによります
04:13
even if you don't make those investments.
たとえ実際には 投資しないとしてもです
04:15
AIDS is the same kind of thing. It's costly to avoid AIDS.
AIDSも同じです AIDSを避けるには犠牲もあります
04:17
People really like to have sex.
だって人は 性交が本当に好きですから
04:20
But, you know, it has a benefit in terms of future longevity.
それでも 避けることでの未来的な利益はあるのです
04:23
But life expectancy in Africa, even without AIDS, is really, really low:
でもアフリカでの平均余命はAIDSがなくてもすごく短いのです
04:29
40 or 50 years in a lot of places.
多くの場所では40年や50年ほどなのです
04:33
I think it's possible, if we think about that intuition, and think about that fact,
直感と事実を照らし合わせると これこそが
04:36
that maybe that explains some of this low behavior change.
行動変化の低さを説明できると思うのです
04:40
But we really need to test that.
でも それを試してみなければなりません
04:43
And a great way to test that is to look across areas in Africa and see:
アフリカ全体を見て
04:45
do people with more life expectancy change their sexual behavior more?
平均余命が長い人々の 性行動の変化を観察するのです
04:48
And the way that I'm going to do that is,
わたしが使う方法では
04:52
I'm going to look across areas with different levels of malaria.
マラリアの有病率が異なる様々な地域を調べます
04:54
So malaria is a disease that kills you.
マラリアも死をもたらす病気であり
04:57
It's a disease that kills a lot of adults in Africa, in addition to a lot of children.
アフリカではたくさんの大人や子供を死に追いやっています
05:00
And so people who live in areas with a lot of malaria
なので マラリアが多い地域の人々の平均余命は
05:03
are going to have lower life expectancy than people who live in areas with limited malaria.
少ない地域の人よりも短いことになります
05:06
So one way to test to see whether we can explain
だから行動変化を平均余命の違いで
05:10
some of this behavior change by differences in life expectancy
説明できるのか試してみるには
05:12
is to look and see is there more behavior change
マラリアの少ない地域で 行動変化が
05:15
in areas where there's less malaria.
もっと起こるのか調べるのです
05:18
So that's what this figure shows you.
それがこのグラフに表れています
05:20
This shows you -- in areas with low malaria, medium malaria, high malaria --
このグラフはマラリアの少ない地域 中位の地域 多い地域で
05:22
what happens to the number of sexual partners as you increase HIV prevalence.
HIVの有病率が増えるにつれての 性交相手の数の推移を表しています
05:26
If you look at the blue line,
青い線を見ると
05:30
the areas with low levels of malaria, you can see in those areas,
マラリアが少ない地域では
05:32
actually, the number of sexual partners is decreasing a lot
実際にHIV有病率があがるにつれて 性交相手の数が
05:35
as HIV prevalence goes up.
大きく減ってきています
05:38
Areas with medium levels of malaria it decreases some --
中位の地域でも減っていますが
05:40
it doesn't decrease as much. And areas with high levels of malaria --
それほどでもありません マラリアが多い地域では
05:42
actually, it's increasing a little bit, although that's not significant.
少しだけですが増えているのがわかります
05:45
This is not just through malaria.
マラリアだけではありません
05:50
Young women who live in areas with high maternal mortality
妊婦死亡率の高い地域に住む若い女性は
05:52
change their behavior less in response to HIV
低い地域に住む女性に比べると
05:55
than young women who live in areas with low maternal mortality.
HIVに対する対応は弱いのです
05:58
There's another risk, and they respond less to this existing risk.
他にもリスクがあると すでにあるリスクにはあまり反応しないのです
06:01
So by itself, I think this tells a lot about how people behave.
なので これで人々がどう行動するのかがわかりますよね
06:06
It tells us something about why we see limited behavior change in Africa.
アフリカでの行動変化の少なさがこれで説明できます
06:09
But it also tells us something about policy.
政策についても分かってきます
06:12
Even if you only cared about AIDS in Africa,
たとえAIDSのことだけを考えていたとしても
06:14
it might still be a good idea to invest in malaria,
マラリア廃絶や
06:17
in combating poor indoor air quality,
室内空気の改善
06:20
in improving maternal mortality rates.
妊産婦死亡率の改善に投資するべきです
06:22
Because if you improve those things,
なぜなら これらの事を改善すると
06:24
then people are going to have an incentive to avoid AIDS on their own.
人々に自分でAIDSを予防しようという動機が生まれるからです
06:26
But it also tells us something about one of these facts that we talked about before.
そして 先ほど話した事について考えて見ましょう
06:30
Education campaigns, like the one that the president is focusing on in his funding,
大統領が注力している教育キャンペーンのようなものですが
06:34
may not be enough, at least not alone.
それだけでは足りません
06:38
If people have no incentive to avoid AIDS on their own,
もし人々にAIDS予防の動機がないのなら
06:40
even if they know everything about the disease,
病気について知っていたとしても
06:42
they still may not change their behavior.
行動を変えないかもしれません
06:44
So the other thing that I think we learn here is that AIDS is not going to fix itself.
ここで AIDSは勝手に消えるものではない事がわかります
06:46
People aren't changing their behavior enough
人は病気を減らすほどには
06:49
to decrease the growth in the epidemic.
行動を変えないのです
06:51
So we're going to need to think about policy
だから 政策について考え
06:54
and what kind of policies might be effective.
効果的な政策を考える必要があります
06:56
And a great way to learn about policy is to look at what worked in the past.
政策について学ぶには 過去の成功例を見るのがいいでしょう
06:58
The reason that we know that the ABC campaign
ウガンダでのABCキャンペーンの成果が
07:01
was effective in Uganda is we have good data on prevalence over time.
わかるのは 数年間の有病率のデータがあったからです
07:03
In Uganda we see the prevalence went down.
ウガンダでは有病率が下がりました
07:06
We know they had this campaign. That's how we learn about what works.
こうして相互関係を知るのです
07:08
It's not the only place we had any interventions.
このような試みはここだけではなく
07:11
Other places have tried things, so why don't we look at those places
ほかの場所でもあったのですが どうして他の場所の有病率に
07:13
and see what happened to their prevalence?
注目しないのでしょうか?
07:17
Unfortunately, there's almost no good data
不幸にも ほかにはいいデータがなく
07:20
on HIV prevalence in the general population in Africa until about 2003.
アフリカの一般人口のHIVの有病率は2003年まで分かりませんでした
07:22
So if I asked you, "Why don't you go and find me
もし「1991年 ブルキナファソでの
07:27
the prevalence in Burkina Faso in 1991?"
有病率のデータを持ってきて」と聞かれても
07:29
You get on Google, you Google, and you find,
Googleで調べて見つかるのは
07:32
actually the only people tested in Burkina Faso in 1991
ブルキナファソで1991年に検査を受けているのは
07:35
are STD patients and pregnant women,
妊婦と性病保有者だけと気づくでしょう
07:38
which is not a terribly representative group of people.
それでは全体の代表にはなりません
07:40
Then if you poked a little more, you looked a little more at what was going on,
もう少し調べて 何が起こっていたのかも調べて見ると
07:42
you'd find that actually that was a pretty good year,
その結果だけでも まだマシだと気づきます
07:45
because in some years the only people tested are IV drug users.
なぜなら 麻薬中毒者しか検査を受けていない年もあるからです
07:48
But even worse -- some years it's only IV drug users,
時には麻薬中毒者だけ
07:51
some years it's only pregnant women.
時には妊婦だけ
07:53
We have no way to figure out what happened over time.
何が起こっていたのか知るすべはないのです
07:55
We have no consistent testing.
一貫した検査がありません
07:57
Now in the last few years, we actually have done some good testing.
過去数年はしっかりと検査を行いました
07:59
In Kenya, in Zambia, and a bunch of countries,
ケニア ザンビア そして多くのほかの国で
08:04
there's been testing in random samples of the population.
一般人口の中で確率標本に基づき検査が行われました
08:07
But this leaves us with a big gap in our knowledge.
しかし それは依然として大きなギャップを残します
08:10
So I can tell you what the prevalence was in Kenya in 2003,
2003年のケニアでの有病率は分かりますが
08:13
but I can't tell you anything about 1993 or 1983.
1983年や1993年のことは何もわかりません
08:16
So this is a problem for policy. It was a problem for my research.
この政策の問題がわたしの研究の障害になりました
08:19
And I started thinking about how else might we figure out
そこで いったいどうすれば過去のアフリカでの有病率を
08:23
what the prevalence of HIV was in Africa in the past.
見つけられるのか考え始めました
08:27
And I think that the answer is, we can look at mortality data,
それに対する答えとして 私は死亡率を調べて
08:29
and we can use mortality data to figure out what the prevalence was in the past.
それを使って過去の有病率を見つけ出すことにしました
08:33
To do this, we're going to have to rely on the fact
そのためには AIDSは特別な種類の病気という
08:37
that AIDS is a very specific kind of disease.
事実に頼ることになります
08:39
It kills people in the prime of their lives.
全盛期の人々に死をもたらすのです
08:41
Not a lot of other diseases have that profile. And you can see here --
そのような病気は多くありません これを見て下さい
08:43
this is a graph of death rates by age in Botswana and Egypt.
これはボツワナとエジプトでの年齢別死亡率のグラフです
08:46
Botswana is a place with a lot of AIDS,
ボツワナはAIDSが多い国で
08:50
Egypt is a place without a lot of AIDS.
エジプトはそうでもありません
08:52
And you see they have pretty similar death rates among young kids and old people.
見て分かるように子供やお年寄りは似たような死亡率ですから
08:54
That suggests it's pretty similar levels of development.
同じ程度であることがわかりますね
08:57
But in this middle region, between 20 and 45,
しかし中程の 20才から45才では
09:00
the death rates in Botswana are much, much, much higher than in Egypt.
ボツワナでの死亡率はエジプトよりも ものすごく高いのです
09:03
But since there are very few other diseases that kill people,
でもほかに死をもたらす病気は多くないので
09:07
we can really attribute that mortality to HIV.
その死亡率がHIVからきていると考えられるのです
09:11
But because people who died this year of AIDS got it a few years ago,
ところが今年AIDSで亡くなったとすると 感染したのは数年前です
09:14
we can use this data on mortality to figure out what HIV prevalence was in the past.
この死亡率を使って過去のHIVの有病率をみつけるのです
09:18
So it turns out, if you use this technique,
この方法を使うと
09:23
actually your estimates of prevalence are very close
実際 有病率の予測は
09:25
to what we get from testing random samples in the population,
一般人口内の確率標本から得た結果とすごく近いのです
09:27
but they're very, very different than what UNAIDS tells us the prevalences are.
しかし国際連合エイズ合同計画(UNAIDS)が発表している有病率とは大きく異なります
09:30
So this is a graph of prevalence estimated by UNAIDS,
これは 1990年代後半におけるアフリカの9つの国での
09:35
and prevalence based on the mortality data
有病率のグラフで 一方はUNAIDSによる予想で
09:38
for the years in the late 1990s in nine countries in Africa.
もう一方は死亡率に基づいたものです
09:40
You can see, almost without exception,
ほとんど例外なしに
09:44
the UNAIDS estimates are much higher than the mortality-based estimates.
UNAIDSの予想は死亡率に基づいたものより 高いですよね
09:46
UNAIDS tell us that the HIV rate in Zambia is 20 percent,
UNAIDSによると ザンビアのHIV率は20%ですが
09:50
and mortality estimates suggest it's only about 5 percent.
死亡率に基づいたものは5%だという予想になっています
09:54
And these are not trivial differences in mortality rates.
死亡率にしてはかなりの違いですよね
09:58
So this is another way to see this.
ほかにも見方があります
10:01
You can see that for the prevalence to be as high as UNAIDS says,
有病率がUNAIDSが言うほど高いのであれば
10:03
we have to really see 60 deaths per 10,000
一万人中60人の死者がないとおかしいのです
10:05
rather than 20 deaths per 10,000 in this age group.
一万人中20人の死者ではおかしいのです
10:07
I'm going to talk a little bit in a minute
これから
10:11
about how we can use this kind of information to learn something
このような情報をどのように使えば
10:13
that's going to help us think about the world.
世界に対する理解が深まるかをお話しします
10:16
But this also tells us that one of these facts
しかし 私が最初のほうに話した事実が
10:18
that I mentioned in the beginning may not be quite right.
正しくないかもしれないと気づくことでしょう
10:20
If you think that 25 million people are infected,
2500万人が感染しているという知識があっても
10:23
if you think that the UNAIDS numbers are much too high,
UNAIDSの数値が高すぎるだけかもしれません
10:25
maybe that's more like 10 or 15 million.
1000万人か1500万人かもしれません
10:28
It doesn't mean that AIDS isn't a problem. It's a gigantic problem.
それはAIDSが問題でないと言うことではありません
大きな問題です
10:30
But it does suggest that that number might be a little big.
だけど 数値が少し高すぎるかもしれないと言うことです
10:34
What I really want to do, is I want to use this new data
大切なのは この新しい情報を使って
10:38
to try to figure out what makes the HIV epidemic grow faster or slower.
何がHIVの流行を早く または遅くさせるのか見つけることなのです
10:40
And I said in the beginning, I wasn't going to tell you about exports.
最初に言ったように 輸出などについては話さない予定でした
10:44
When I started working on these projects,
このプロジェクトを始めた時に
10:47
I was not thinking at all about economics,
経済が関わるとは思わなかったのですが
10:49
but eventually it kind of sucks you back in.
だんだん考えさせられるようになったのです
10:51
So I am going to talk about exports and prices.
なのでやはり 輸出と価格の話をしますね
10:54
And I want to talk about the relationship between economic activity,
そして経済活動 特に
10:57
in particular export volume, and HIV infections.
輸出量とHIV感染の関係について話します
11:00
So obviously, as an economist, I'm deeply familiar
経済学者としての私がはっきりと言えるのは
11:04
with the fact that development, that openness to trade,
発展や自由貿易が発展途上国にとって
11:08
is really good for developing countries.
とてもいいということです
11:10
It's good for improving people's lives.
人々の生活を改善します
11:12
But openness and inter-connectedness, it comes with a cost
でも開放性や相互接続性は 病気の観点からは
11:15
when we think about disease. I don't think this should be a surprise.
デメリットもあるのです 驚くことではありません
11:17
On Wednesday, I learned from Laurie Garrett
水曜日にローリー・ギャレットから
11:20
that I'm definitely going to get the bird flu,
絶対に鳥インフルにかかると言われましたが
11:22
and I wouldn't be at all worried about that
アジアとの関わりがないので
11:24
if we never had any contact with Asia.
全く心配していません
11:27
And HIV is actually particularly closely linked to transit.
HIVも交通との深い関係があるんです
11:30
The epidemic was introduced to the US
流行病が最初にアメリカに知れ渡ったのは
11:34
by actually one male steward on an airline flight,
飛行機のある男性乗務員がアフリカ滞在中に感染し
11:36
who got the disease in Africa and brought it back.
アメリカに持ち帰ったからなのです
11:40
And that was the genesis of the entire epidemic in the US.
それがアメリカで流行することのきっかけになったのです
11:42
In Africa, epidemiologists have noted for a long time
アフリカでは 伝染病学者が長い間にわたって
11:45
that truck drivers and migrants are more likely to be infected than other people.
トラック運転手や移民は他の人より感染している可能性が高いと言い続けていました
11:49
Areas with a lot of economic activity --
経済活動が盛んで
11:53
with a lot of roads, with a lot of urbanization --
道があり 都市化している
11:55
those areas have higher prevalence than others.
地域では他より有病率も高いのです
11:58
But that actually doesn't mean at all
しかしそれは 輸出や貿易の増加と
12:00
that if we gave people more exports, more trade, that that would increase prevalence.
有病率の増加とを結びつけているわけではありません
12:02
By using this new data, using this information about prevalence over time,
長期間に渡る有病率の この新しいデータや情報を使って
12:06
we can actually test that. And so it seems to be --
それを試すことができるのです そうすると
12:10
fortunately, I think -- it seems to be the case
幸運にも
12:14
that these things are positively related.
その関係性が見えてきます
12:16
More exports means more AIDS. And that effect is really big.
輸出が多ければAIDSも多く その影響はかなり大きいのです
12:18
So the data that I have suggests that if you double export volume,
このデータによると もし輸出量を2倍に増やすと
12:22
it will lead to a quadrupling of new HIV infections.
新規のHIV感染は4倍にも増えるのです
12:26
So this has important implications both for forecasting and for policy.
これは予測および政策に大きく影響を及ぼします
12:31
From a forecasting perspective, if we know where trade is likely to change,
予測の観点から言うと もし貿易が変わるような出来事
12:34
for example, because of the African Growth and Opportunities Act
例えばアフリカ成長機会法や
12:38
or other policies that encourage trade,
他の貿易支援の政策を知っていれば
12:41
we can actually think about which areas are likely to be heavily infected with HIV.
実際にどの地域がHIV感染の危険にさらされるかが考えつきます
12:43
And we can go and we can try to have pre-emptive preventive measures there.
そして そういった地域に行って感染前の予防ができるのです
12:48
Likewise, as we're developing policies to try to encourage exports,
同じように 輸出支援の政策を展開する上で
12:54
if we know there's this externality --
輸出の増加に伴って起こる
12:57
this extra thing that's going to happen as we increase exports --
外部性の存在を知っていれば
12:59
we can think about what the right kinds of policies are.
適切な政策が何か考えられるのです
13:01
But it also tells us something about one of these things that we think that we know.
そして私たちが知っていると思い込んでいることについても気づくことがあります
13:04
Even though it is the case that poverty is linked to AIDS,
貧困とAIDSは関わっていますよね
13:07
in the sense that Africa is poor and they have a lot of AIDS,
特にアフリカは貧乏でAIDSが多いです
13:10
it's not necessarily the case that improving poverty -- at least in the short run,
ですが 少なくとも短期間では貧困を改善したり
13:13
that improving exports and improving development --
輸出や発展を援助するということが
13:17
it's not necessarily the case that that's going to lead
必ずしも HIV有病率を
13:19
to a decline in HIV prevalence.
減らすわけでわありません
13:21
So throughout this talk I've mentioned a few times
今までウガンダの
13:24
the special case of Uganda, and the fact that
ケーススタディと
13:26
it's the only country in sub-Saharan Africa with successful prevention.
サブサハラ・アフリカで唯一予防に成功していることをお話しました
13:28
It's been widely heralded.
それは広く認知されています
13:32
It's been replicated in Kenya, and Tanzania, and South Africa and many other places.
ケニアやタンザニア 南アフリカなど他の場所でも多く模倣されています
13:34
But now I want to actually also question that.
しかし ここでそれを疑問視してみたいのです
13:40
Because it is true that there was a decline in prevalence
なぜなら1990年代にウガンダで有病率に
13:44
in Uganda in the 1990s. It's true that they had an education campaign.
減少傾向が見られたのは本当で 教育キャンペーンをしたのも本当ですが
13:47
But there was actually something else that happened in Uganda in this period.
同時期にウガンダでは他のことが起こっていたのです
13:51
There was a big decline in coffee prices.
コーヒーの値段が大きく下がったのです
13:57
Coffee is Uganda's major export.
コーヒーはウガンダの主要な輸出品です
13:59
Their exports went down a lot in the early 1990s -- and actually that decline lines up
その輸出が1990年代前半にガクッと下がり そしてその価格減少と今回の
14:01
really, really closely with this decline in new HIV infections.
HIV新規感染数の減少が絶妙に並行して起こっていたのです
14:06
So you can see that both of these series --
これを見て下さい
14:10
the black line is export value, the red line is new HIV infections --
黒い線が輸出額 赤い線がHIV新規感染数です
14:13
you can see they're both increasing.
両方とも上昇しているのがわかると思います
14:16
Starting about 1987 they're both going down a lot.
1987年位から両方とも大きく下降しており
14:18
And then actually they track each other
そしてお互いを追うようにして
14:20
a little bit on the increase later in the decade.
後半に少し上昇しています
14:22
So if you combine the intuition in this figure
この図から受ける直感と
14:24
with some of the data that I talked about before,
さきほどのデータを掛け合わせると
14:26
it suggests that somewhere between 25 percent and 50 percent
ウガンダで見られた有病率の減少のうち
14:29
of the decline in prevalence in Uganda
25%から50%は
14:33
actually would have happened even without any education campaign.
教育キャンペーンなしでも起こったのではないかと推測できます
14:35
But that's enormously important for policy.
これは政策にとって とても大切なことです
14:39
We're spending so much money to try to replicate this campaign.
このキャンペーンを模倣するために多額のお金がかけられているのです
14:41
And if it was only 50 percent as effective as we think that it was,
政策が半分くらいしか効果がないとすれば
14:43
then there are all sorts of other things
他にもいろいろと
14:46
maybe we should be spending our money on instead.
お金をかけるべき事があるはずです
14:48
Trying to change transmission rates by treating other sexually transmitted diseases.
他の性病を治療したり 男性への割礼を行うことで
14:50
Trying to change them by engaging in male circumcision.
感染率を変えてみる事もできます
14:54
There are tons of other things that we should think about doing.
他にも考えるべきことはたくさんあります
14:56
And maybe this tells us that we should be thinking more about those things.
もしかすると こういったことをもっと考えるのが大切だと気づかせてくれるかも知れません
14:58
I hope that in the last 16 minutes I've told you something that you didn't know about AIDS,
16分の私の話で AIDSについて初めて知ったこと そして
15:02
and I hope that I've gotten you questioning a little bit
知っていたつもりでも疑問になったことが
15:07
some of the things that you did know.
あれば嬉しいです
15:09
And I hope that I've convinced you maybe
そして みなさんが
15:11
that it's important to understand things about the epidemic
政策を考える上で 流行病について学ぶのは
15:13
in order to think about policy.
大切だと納得していただければ光栄です
15:15
But more than anything, you know, I'm an academic.
しかし何より わたしは学者です
15:18
And when I leave here, I'm going to go back
この場を去れば わたしは自分の
15:20
and sit in my tiny office, and my computer, and my data.
小さなオフィスのコンピューターとデータに戻っていくのです
15:22
And the thing that's most exciting about that
そして一番興奮するのが
15:25
is every time I think about research, there are more questions.
研究のことを考えるたびに質問が次々あることです
15:27
There are more things that I think that I want to do.
私がやりたいと思う事はもっとあるのです
15:30
And what's really, really great about being here
ここにいてすばらしいと思うのは
15:32
is I'm sure that the questions that you guys have
みなさんが抱えている質問が
15:34
are very, very different than the questions that I think up myself.
私が抱えているものと全く違うということです
15:36
And I can't wait to hear about what they are.
それが何かを聞くのが楽しみでなりません
15:39
So thank you very much.
本当にありがとうございました
15:41
Translator:Hikari Fukuda
Reviewer:Shogo Kobayashi

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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.

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 >>

 

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