20:32
TEDGlobal 2005

Steven Levitt: Surprising stats about child carseats

スティーヴン・レヴィット: チャイルド・シートにまつわる統計

Filmed:

車における死亡事故から子供を守るにはチャイルド・シートはシートベルトと同じ程度の効果しかないというデータをスティーヴン・レヴィットが示す。Q&Aでも重要な指摘をしている。

- Economist
Steven Levitt's eye-opening Freakonomics took economic theory into the real world of suburban parenting and urban drug gangs, turning conventional wisdom upside-down. Full bio

Once upon a time, there was a dread disease that afflicted children.
昔、子供達を苦しめる とても恐ろしい病気がありました
00:18
And in fact, among all the diseases that existed in this land,
実際 地球上の病気の中で最も重篤なもので
00:23
it was the worst. It killed the most children.
多くの子供が亡くなりました
00:27
And along came a brilliant inventor, a scientist,
そこに賢明な科学者が現れ
00:30
who came up with a partial cure for that disease.
不完全ながらも治療法を発明しました
00:33
And it wasn't perfect. Many children still died,
それは完璧なものではなく、尚多くの命が失われましたが
00:36
but it was certainly better than what they had before.
以前より状況が改善しました
00:40
And one of the good things about this cure was that it was free,
その治療法の利点の一つはそれがタダということでした
00:43
virtually free, and was very easy to use.
文字通り無料である上に 使い方は簡単でした
00:49
But the worst thing about it was that you couldn't use it
しかし 最大の難点は
00:51
on the youngest children, on infants, and on one-year-olds.
2歳以下の赤ん坊には使えないことでした
00:54
And so, as a consequence, a few years later,
そして数年後に
00:58
another scientist -- perhaps maybe this scientist
別の科学者が現れました
01:00
not quite as brilliant as the one who had preceded him,
先人ほど賢明でなかったようです
01:02
but building on the invention of the first one --
しかし 第1の治療法を改良して
01:06
came up with a second cure.
第2の治療法を見つけました
01:08
And the beauty of the second cure for this disease
第2の治療法の素晴らしい点は
01:11
was that it could be used on infants and one-year-olds.
2歳未満の赤ん坊にも治療できたことです
01:14
And the problem with this cure was it was very expensive,
しかしこの治療の問題は 高価な点でした
01:18
and it was very complicated to use.
そして 使用法も複雑でした
01:23
And although parents tried as hard as they could to use it properly,
親は適切な使用を心がけましたが
01:24
almost all of them ended up using it wrong in the end.
うまく使える人はほとんどいませんでした
01:28
But what they did, of course, since it was so complicated and expensive,
第2の治療法は複雑で高価だったので
01:32
they only used it on the zero-year-olds and the one-year-olds.
2歳未満の子供たちにのみ用いられました
01:35
And they kept on using the existing cure that they had
2歳以上の子供には
01:38
on the two-year-olds and up.
以前の治療法を使い続けました
01:41
And this went on for quite some time. People were happy.
人々はしばらくこの方法に満足していました
01:42
They had their two cures. Until a particular mother,
ある母親が2歳になったばかりの子を失うまで
01:44
whose child had just turned two, died of this disease.
2つの治療方法を併用していました
01:47
And she thought to herself, "My child just turned two,
母親は考えました
あの子は2歳になったところだった
01:52
and until the child turned two, I had always used
2歳になるまでは
01:56
this complicated, expensive cure, you know, this treatment.
複雑で高価な治療法を使い続けてきた
02:00
And then the child turned two, and I started using
そして2歳になり
02:05
the cheap and easy treatment, and I wonder" --
安価で簡単な治療法に変えたばかりだった
02:06
and she wondered, like all parents who lose children wonder --
そして 子を失った他の親と同様に悩みます
02:09
"if there isn't something that I could have done,
他の方法はなかったのだろうか
02:11
like keep on using that complicated, expensive cure."
複雑で高価な治療法を使い続けた方がよかったのか
02:13
And she told all the other people, and she said,
母親は皆にその思いを語りました
02:17
"How could it possibly be that something
「本当にこんなことがあり得るのでしょうか?
02:20
that's cheap and simple works as well as something
安価で単純な方法が
02:22
that's complicated and expensive?"
あの複雑で高価な治療法と同じ効果があるなんて」
02:25
And the people thought, "You know, you're right.
周りの人も同じ考えを持っていました
02:27
It probably is the wrong thing to do to switch
安価で単純な方法に切り替えたことが
02:29
and use the cheap and simple solution."
間違いだったのかもしれない
02:31
And the government, they heard her story and the other people,
政府も母親たちの話を聞いて言いました
02:34
and they said, "Yeah, you're right, we should make a law.
新しい法律をつくるべきだ
02:37
We should outlaw this cheap and simple treatment
この安価で単純な治療法を違法にすべきだ
02:40
and not let anybody use this on their children."
子供たちにこの治療法を用いてはならない
02:42
And the people were happy. They were satisfied.
人々はそれに満足しました
02:45
For many years this went along, and everything was fine.
それから何年間かはうまくいっていました
02:47
But then along came a lowly economist, who had children himself,
ある時ひとりの無名の経済学者が現れました
02:50
and he used the expensive and complicated treatment.
彼にも子供がおり高価で複雑な治療法を利用していました
02:55
But he knew about the cheap and simple one.
しかし安価で単純な治療法も知っていました
03:02
And he thought about it, and the expensive one
彼にとっては高価な治療法が
03:04
didn't seem that great to him. So he thought,
それほど優れているとは思えませんでした
03:06
"I don't know anything about science, but I do know something about data,
私は科学は無知だが データについては知識はある
03:09
so maybe I should go and look at the data
データを調べてみよう
03:12
and see whether this expensive and complicated treatment
この高価で複雑な治療法が
03:14
actually works any better than the cheap and simple one."
安価で単純な治療法より効果があるか確かめよう
03:18
And lo and behold, when he went through the data,
データを調べると 驚いたことに
03:21
he found that it didn't look like the expensive, complicated
少なくとも2歳以上の子供については
03:23
solution was any better than the cheap one,
高価で複雑な治療法が 安価な治療法よりも
03:26
at least for the children who were two and older --
効果が優れているわけではありませんでした
03:29
the cheap one still didn't work on the kids who were younger.
2歳未満の子供には 安価な治療法はやはり無効でした
03:31
And so, he went forth to the people and he said,
経済学者は人々に言いました
03:34
"I've made this wonderful finding:
すばらしい発見をしました
03:38
it looks as if we could just use the cheap and simple solution,
安価で簡単な方法だけで問題ないようだ
03:40
and by doing so we could save ourselves 300 million dollars a year,
その結果 年間3億ドルの経費を削減できる
03:43
and we could spend that on our children in other ways."
そのお金を子供のための別のことに使おう
03:46
And the parents were very unhappy, and they said,
親たちは非常に不満に思いました
03:48
"This is a terrible thing, because how can the cheap and easy thing
安価で簡単な方法が厄介な方法と同じ効果があるとは思えない
03:52
be as good as the hard thing?" And the government was very upset.
政府も非常に立腹しました
03:54
And in particular, the people who made this expensive solution
特にこの高価な方法を見出した人は
03:58
were very upset because they thought,
この考えを腹立たしく思いました
04:01
"How can we hope to compete with something that's essentially free?
ほぼ無料ともいえる方法に取って代わられると
04:03
We would lose all of our market."
市場から閉め出されてしまう
04:06
And people were very angry, and they called him horrible names.
人々も怒り 経済学者を非難しました
04:08
And he decided that maybe he should leave the country
経済学者は 数日 国を離れるべきだと考えました
04:11
for a few days, and seek out some more intelligent,
そして より賢明で心の広い人が住む
04:14
open-minded people in a place called Oxford,
オックスフォードと呼ばれる場所へ行き
04:18
and come and try and tell the story at that place.
その地で自分の考えを伝えようとしたのです
04:21
And so, anyway, here I am. It's not a fairy tale.
私がここにいるのはそのためです
おとぎ話ではありません
04:24
It's a true story about the United States today,
これがアメリカの現状です
04:28
and the disease I'm referring to is actually
今まで話してきた病気とは つまり
04:30
motor vehicle accidents for children.
子供の交通事故です
04:33
And the free cure is adult seatbelts, and the expensive cure --
無料の治療法とは大人用のシートベルトで
04:36
the 300-million-dollar-a-year cure -- is child car seats.
年間3億ドルに相当する高価な治療法とはチャイルドシートです
04:42
And what I'd like to talk to you about today
これが事実であると私が信じるに至った証拠について
04:46
is some of the evidence why I believe this to be true:
今日はお話ししたいと思います
04:48
that for children two years old and up,
2歳以上の子供はチャイルドシートを使っても
04:51
there really is no real benefit -- proven benefit -- of car seats,
安全は約束されません
04:53
in spite of the incredible energy
多大なエネルギーを使って
04:58
that has been devoted toward expanding the laws
この法律を普及させてきました
05:03
and making it socially unacceptable
子供にシートベルトを使うことを
05:06
to put your children into seatbelts. And then talk about why --
禁じました
それが正しいとされてきた理由について
05:08
what is it that makes that true?
説明します
05:13
And then, finally talk a little bit about a third way,
最後に 第3の方法について触れたいと思います
05:14
about another technology, which is probably better than anything we have,
それはどれよりも優れたものです
05:17
but which -- there hasn't been any enthusiasm for adoption
しかし 採り入れようとする人はいません
05:20
precisely because people are so enamored
なぜなら 人々は
05:23
with the current car seat solution. OK.
チャイルドシートが最善と思っているからです
05:25
So, many times when you try to do research on data,
さて データ調査では
05:28
it records complicated stories -- it's hard to find in the data.
複雑な事象の記録が基になりますが、
05:31
It doesn't turn out to be the case when you look at seatbelts versus car seats.
シートベルトとチャイルド シートの比較はそうではありません
05:35
So the United States keeps a data set
1975年以降に発生したすべての死亡事故について
05:38
of every fatal accident that's happened since 1975.
米国ではそのデータを記録しています
05:40
So in every car crash in which at least one person dies,
つまり死亡者があった自動車事故について
05:43
they have information on all of the people.
同乗者の情報を得ることができるのです
05:46
So if you look at that data -- it's right up on the National Highway
運輸省道路交通安全局のサイトを
05:48
Transportation Safety Administration's website --
ご覧ください
05:51
you can just look at the raw data,
未加工のデータをご覧になるだけでも
05:53
and begin to get a sense of the limited amount of evidence
2歳以上の子供のチャイルドシート利用を支持する証拠が
05:55
that's in favor of car seats for children aged two and up.
わずかしかないことが 理解いただけるでしょう
05:59
So, here is the data. Here I have, among two- to six-year-olds --
6歳以上はチャイルドシートは使わないので
06:02
anyone above six, basically no one uses car seats,
2歳から6歳までの子供が同乗して死亡事故が発生した場合です
06:06
so you can't compare -- 29.3 percent of the children who are unrestrained
そのうち器具で固定されていなかった場合
06:08
in a crash in which at least one person dies, themselves die.
29.3パーセントの子供が死亡しています
06:14
If you put a child in a car seat, 18.2 percent of the children die.
チャイルドシートに座った子供の死亡率は18.2パーセント
06:18
If they're wearing a lap-and-shoulder belt, in this raw data,
もし3点式ベルトをしていれば死亡率は19.4パーセントです
06:23
19.4 percent die. And interestingly, wearing a lap-only seatbelt,
2点式ベルト着用では16.7パーセントでした
06:25
16.7 percent die. And actually, the theory tells you
理論的には
06:30
that the lap-only seatbelt's got to be worse
2点式シートベルトは 3点式よりよくないはずです
06:32
than the lap-and-shoulder belt. And that just reminds you
未加工のデータを処理する際には
06:35
that when you deal with raw data, there are hundreds
非常に多くの変数が存在します
06:36
of confounding variables that may be getting in the way.
それが結果をわかりにくくしています
06:38
So what we do in the study is -- and this is just presenting
そこで私たちの研究においては
06:41
the same information, but turned into a figure to make it easier.
より簡単に理解できる図を作成しています
06:46
So the yellow bar represents car seats,
黄色のバーがチャイルド シート
06:49
the orange bar lap-and-shoulder, and the red bar lap-only seatbelts.
オレンジは3点式 赤色が2点式のシートベルトを示しています
06:52
And this is all relative to unrestrained --
どれも着用していない場合との比較です
06:56
the bigger the bar, the better. Okay.
バーが長いほど 優秀ということになります
06:58
So, this is the data I just showed, OK?
それでは このデータにご注目ください
06:59
So the highest bar is what you're striving to beat.
最も長いバーこそ 誰もが求めているものです
07:01
So you can control for the basic things, like how hard the crash was,
衝突時の衝撃の大きさや
07:04
what seat the child was sitting in, etc., the age of the child.
子供が座っていた座席 年齢も調整できます
07:08
And that's that middle set of bars.
真ん中のグラフにあたります
07:12
And so, you can see that the lap-only seatbelts
このような調整をおこなうと
07:14
start to look worse once you do that.
2点式が あまり良いとは思えなくなります
07:17
And then finally, the last set of bars,
そして最後に この最後のグラフです
07:19
which are really controlling for everything
このバーは 衝突事故において想定できるすべての要素を
07:21
you could possibly imagine about the crash,
調整したものです
07:24
50, 75, 100 different characteristics of the crash.
衝突事故には様々な特徴があります
07:26
And what you find is that the car seats and the lap-and-shoulder belts,
命を守るという観点ではチャイルドシートと三点式ベルトは
07:29
when it comes to saving lives, fatalities look exactly identical.
死亡率は全く同時であることがわかります
07:32
And the standard error bands are relatively small around these estimates as well.
ばらつき幅はこの推定でも
比較的小さいものです
07:36
And it's not just overall. It's very robust
ざっくりとした数値ではありません
07:40
to anything you want to look at.
非常にはっきりと傾向がわかります
07:43
One thing that's interesting: if you look at frontal-impact crashes --
興味深いことに
07:45
when the car crashes, the front hits into something --
正面衝突のケースでは
07:48
indeed, what you see is that the car seats look a little bit better.
チャイルド シートの方が有効です
07:51
And I think this isn't just chance.
これは偶然ではありません
07:55
In order to have the car seat approved,
チャイルドシートが承認されるためには
07:57
you need to pass certain federal standards,
連邦規格に合格する必要があるからです
07:58
all of which involve slamming your car into a direct frontal crash.
すなわち 正面衝突も考慮する必要があるのです
08:01
But when you look at other types of crashes, like rear-impact crashes,
しかし 後部からの衝突では
08:06
indeed, the car seats don't perform as well.
チャイルドシートはそれほど有効ではありません
08:08
And I think that's because they've been optimized to pass,
テストに合格することに重点を置いているのです
08:11
as we always expect people to do,
我々が常に期待するように
08:13
to optimize relative to bright-line rules
明確な判断基準を満たす事を優先しているからです
08:15
about how affected the car will be.
車がどれほど影響を受けるかということです
08:17
And the other thing you might argue is,
もう1点についてはこう議論されるでしょう
08:21
"Well, car seats have got a lot better over time.
チャイルドシートの性能が向上しているはずだ
08:22
And so if we look at recent crashes --
最近の衝突事故に限って数値を見ようとしても
08:24
the whole data set is almost 30 years' worth of data --
最近の事故に限定されてはいません
08:27
you won't see it in the recent crashes. The new car seats are far, far better."
データは過去30年にわたるものだからです
08:29
But indeed, in recent crashes the lap-and-shoulder seatbelts,
しかし 最近の事故でも 三点式ベルトは
08:31
actually, are doing even better than the car seats.
チャイルドシートより有効です
08:35
They say, "Well, that's impossible, that can't be."
そんなはずはない と思う人もいるでしょう
08:38
And the line of argument, if you ask parents, is,
子供たちの親はこう言います
08:41
"But car seats are so expensive and complicated,
チャイルドシートは高価で複雑だ
08:43
and they have this big tangle of latches,
掛け金が絡み合っているし
08:46
how could they possibly not work better than seatbelts
シートベルトよりも効果がないはずがない
08:49
because they are so expensive and complicated?"
高価で複雑なのだから
08:52
It's kind of an interesting logic,
非常に興味深い論理です
08:54
I think, that people use. And the other logic, they say,
別の論理もあります
08:57
"Well, the government wouldn't have told us [to] use them
チャイルドシートがその程度のものなら
09:00
if they weren't much better."
それを使えと政府が言うはずがない
09:02
But what's interesting is the government telling us to use them
しかし政府が利用を促しているのは
09:04
is not actually based on very much.
データを元にしているのではありません
09:06
It really is based on some impassioned pleas of parents
2歳になったばかりの子供を失った親たちの
09:08
whose children died after they turned two,
強い願いに基づいているのです
09:11
which has led to the passage of all these laws -- not very much on data.
その願いが一連の法律を通過させました
09:14
So you can only get so far, I think, in telling your story
ここまでのところ
抽象的な統計の数字で
09:18
by using these abstract statistics.
お話ししてきました
09:22
And so I had some friends over to dinner, and I was asking --
友人を数人 夕食に招いた時
09:24
we had a cookout -- I was asking them what advice they might have for me
私はアドバイスを求めました
09:29
about proving my point. They said, "Why don't you run some crash tests?"
衝突実験をするといい と言われました
09:32
And I said, "That's a great idea."
いい考えだと思いました
09:36
So we actually tried to commission some crash tests.
実際に衝突実験を行いました
09:38
And it turns out that as we called around to the independent
衝突テストを行う独立系の会社を
09:40
crash test companies around the country,
探し歩きました
09:45
none of them wanted to do our crash test
衝突テストを引き受けてくれる会社はありませんでした
09:48
because they said, some explicitly, some not so explicitly,
なぜなら
09:50
"All of our business comes from car seat manufacturers.
チャイルド シートの製造元から仕事をもらっているからです
09:54
We can't risk alienating them by testing seatbelts relative to car seats."
シートベルトとの比較実験で関係を悪くしたくないのです
09:56
Now, eventually, one did. Under the conditions of anonymity,
なんとか 匿名を条件に
10:00
they said they would be happy to do this test for us --
実験をしてくれる会社を見つけました
10:04
so anonymity, and 1,500 dollars per seat that we crashed.
衝突させる度に1席あたり1500ドル
10:07
And so, we went to Buffalo, New York,
ニューヨーク州 バッファローを訪れました
10:12
and here is the precursor to it.
彼等が先発隊です
10:14
These are the crash test dummies,
衝突テスト用のダミーです
10:16
waiting for their chance to take the center stage.
センター ステージにあがろうと 出番を待っています
10:18
And then, here's how the crash test works.
衝突テストの模様です
10:21
Here, they don't actually crash the entire car, you know --
車1台をまるごと衝突させるわけではありません
10:23
it's not worth ruining a whole car to do it.
その必要はないのです
10:26
So they just have these bench seats,
ベンチシートだけあります
10:29
and they strap the car seat and the seatbelt onto it.
そこにシートベルトを締めチャイルド シートをのせます
10:30
So I just wanted you to look at this.
こちらをご覧ください
10:32
And I think this gives you a good idea of why parents think
親は チャイルド シートが有効と考える理由がわかります
10:34
car seats are so great. Look at the kid in the car seat.
チャイルド シートに座っている子を見て下さい
10:36
Does he not look content, ready to go,
何があっても生き残るように見えますね?
10:38
like he could survive anything? And then, if you look at the kid in back,
一方で後部座席の子供は
10:41
it looks like he's already choking before the crash even happens.
衝突が起こる前だというのに 窒息しそうではありませんか
10:43
It's hard to believe, when you look at this, that
衝突が起きたとき 後部座席の子供が
10:46
that kid in back is going to do very well when you get in a crash.
無事で済むとは信じがたいです
10:49
So this is going to be a crash
さて衝突実験を行います
10:51
where they're going to slam this thing forward into a wall
時速50キロで壁に向かって衝突させると
10:53
at 30 miles an hour, and see what happens. OK?
何が起こるか見てみましょう
10:56
So, let me show you what happens.
さて何が起こるのでしょうか
10:59
These are three-year-old dummies, by the way.
ちなみに このダミーは3歳児です
11:01
So here -- this is the car seat. Now watch two things:
こちらはチャイルド シートです 2つの点に注目してください
11:04
watch how the head goes forward,
頭が前方に飛び出し
11:06
and basically hits the knees -- and this is in the car seat --
膝にぶつかりそうになります これがチャイルド シートです
11:08
and watch how the car seat flies around, in the rebound, up in the air.
チャイルドシートがあちこち跳ねています
11:10
The car seat's moving all over the place.
チャイルドシートは あらゆる方向に動きます
11:15
Bear in mind there are two things about this.
2つのことに注意しておいてください
11:17
This is a car seat that was installed by someone
このチャイルドシートを取り付けたのは
11:19
who has installed 1,000 car seats, who knew exactly how to do it.
経験豊富で正しく設置できる人です
11:22
And also it turned out these bench seats
また このベンチシートは
11:25
are the very best way to install car seats.
チャイルドシートの取り付けにには最適なのです
11:26
Having a flat back makes it much easier to install them.
背部が平面なので取り付けが簡単です
11:29
And so this is a test that's very much rigged in favor of the car seat,
このテストはチャイルドシートに有利な条件で行われました
11:32
OK? So, that kid in this crash fared very well.
この衝突事故にあった子供は よく頑張りました
11:35
The federal standards are
連邦規格では
11:38
that you have to score below a 1,000
チャイルドシートとして認定を受けるには
11:40
to be an approved car seat on this crash,
1000以下のスコアでなければなりません
11:42
in some metric of units which are not important.
この際 単位は重要ではありません
11:44
And this crash would have been about a 450.
この衝突実験では スコアは450でした
11:48
So this car seat was actually an above-average car seat
消費者レポートでは このチャイルド シートは
11:51
from Consumer Reports, and did quite well.
平均以上の数値でした
11:53
So the next one. Now, this is the kid, same crash,
次は シートベルトを着けている人形を使います
11:55
who is in the seatbelt. He hardly moves at all, actually,
他の人形ほど動きません
11:58
relative to the other child. The funny thing is,
おもしろいことに
12:03
the cam work is terrible because they've only set it up
カメラワークが悪かったのです
12:06
to do the car seats, and so, they actually don't even have a way
チャイルドシートと同じ設定だったので
12:09
to move the camera so you can see the kid that's on the rebound.
子供が弾んでいる様子を撮影することさえできませんでした
12:11
Anyway, it turns out that those two crashes, that actually
この3歳の子供に関して行った2度の衝突では
12:13
the three-year-old did slightly worse. So, he gets about a 500
スコアは約500でした
12:17
out of -- you know, on this range -- relative to a 400 and something.
先ほどと比較すると良くない結果でした
12:21
But still, if you just took that data from that crash
この衝突でのデータを連邦政府に持っていくとします
12:25
to the federal government, and said, "I have invented a new car seat.
新しいチャイルド シートを発明したので
12:28
I would like you to approve it for selling,"
販売する為の承認を得たいと言います
12:31
then they would say, "This is a fantastic new car seat, it works great.
すばらしいチャイルドシートだ と言うでしょう
12:34
It only got a 500, it could have gotten as high up as a 1,000."
スコアは500でした
1000までは問題ないのです
12:37
And this seatbelt would have passed with flying colors
このシートベルトは チャイルドシートとして
12:39
into being approved as a car seat.
何の問題もなく承認を受けたはずです
12:42
So, in some sense, what this is suggesting
この実験が示していることは
12:44
is that it's not just that people are setting up their car seats wrong,
単にチャイルドシートのセット方法に誤りがあって
12:46
which is putting children at risk. It's just that, fundamentally,
子供たちを危険にさらしてしまっているのではなく
12:49
the car seats aren't doing much.
チャイルドシートでは十分ではないのです
12:51
So here's the crash. So these are timed at the same time,
タイミングをあわせてあります
12:53
so you can see that it takes much longer with the car seat --
チャイルドシートの方がリバウンドを続けています
12:55
at rebound, it takes a lot longer --
ずっと長くです
12:57
but there's just a lot less movement for child who's in the seatbelt.
シートベルト着用の子供の方が動きが小さいです
12:59
So, I'll show you the six-year-old crashes as well.
6歳児の衝突についてもご覧ください
13:03
The six-year-old is in a car seat, and it turns out
チャイルド シートに座った6歳児です
13:05
that looks terrible, but that's great. That's like a 400, OK?
数値は400程度でしょうか
13:10
So that kid would do fine in the crash.
つまり衝突でも無事だということです
13:15
Nothing about that would have been problematic to the child at all.
この衝突では子供に問題が生じることは全くないでしょう
13:16
And then here's the six-year-old in the seatbelt,
次はシートベルト着用の6歳児です
13:20
and in fact, they get exactly within, you know,
数値は数ポイント違いますが ほとんど同じ結果です
13:23
within one or two points of the same. So really, for the six-year-old,
つまり 6歳児に関しては
13:25
the car seat did absolutely nothing whatsoever.
チャイルド シート固有の効果はありません
13:29
That's some more evidence, so in some sense --
この他にも いくつか証拠はあります
13:33
I was criticized by a scientist, who said, "You could never publish
しかしある科学者から批判をいただきました
13:36
a study with an n of 4," meaning those four crashes.
4回の実験だけで研究成果を公表すべきではない と
13:40
So I wrote him back and I said, "What about an n of 45,004?"
彼に45004回のテストであれば どうでしょうか? と返信しました
13:42
Because I had the other 45,000 other real-world crashes.
実際に発生した45000回の衝突事故も考慮しているのです
13:46
And I just think that it's interesting that the idea
実際に発生した衝突事故のデータを使うという発想も
13:48
of using real-world crashes, which is very much something
良いのではないかと思います
13:52
that economists think would be the right thing to do,
経済学者は 真っ当な方法だと考えます
13:54
is something that scientists don't actually, usually think --
しかし 科学者は
13:56
they would rather use a laboratory,
実験室を使うことを考えるでしょう
13:58
a very imperfect science of looking at the dummies,
それは代替品を使った 非常に不完全な科学です
14:01
than actually 30 years of data of what we've seen
我々が検証した子供とチャイルド シートに関する
14:03
with children and with car seats.
30年間にわたるデータと異なります
14:07
And so I think the answer to this puzzle
この問題に対して
14:10
is that there's a much better solution out there,
遙かによい解決方法があるでしょう
14:14
that's gotten nobody excited because everyone
チャイルドシートが上手くいっているように思えるので
14:17
is so delighted with the way car seats are presumably working.
その解決方法を誰も受け入れないのです
14:20
And if you think from a design perspective,
デザインの観点から考えるのであれば
14:24
about going back to square one, and say,
最初に立ち戻って考え こう言うでしょう
14:27
"I just want to protect kids in the back seat."
「後部座席の子供を守りたいんだ」
14:29
I don't there's anyone in this room who'd say,
ここに おられる方で こんな風におっしゃる方はいないでしょう
14:31
"Well, the right way to start would be,
「まず最初に
14:33
let's make a great seat belt for adults.
大人用の高性能シートベルトをつくるのが先決だ
14:34
And then, let's make this really big contraption
その後で なんとかして
14:37
that you have to rig up to it in this daisy chain."
その複雑な装置を取り付けるようにしようじゃないか」
14:39
I mean, why not start -- who's sitting in the back seat anyway except for kids?
でも、後部座席に乗るのは主に子供たちですよね
14:42
But essentially, do something like this,
つまりは この通りです
14:45
which I don't know exactly how much it would cost to do,
費用は分かりません
14:48
but there's no reason I could see
でも 普通の座席より 高価である理由は
14:50
why this should be much more expensive than a regular car seat.
見つからないでしょう
14:51
It's just actually -- you see, this is folding up -- it's behind the seat.
この座席は折りたたみ式で
座席の背もたれです
14:53
You've got a regular seat for adults, and then you fold it down,
大人用の普通の座席があるところに
これを展開すると
14:57
and the kid sits on top, and it's integrated.
子供たちの座る座席になります
14:59
It seems to me that this can't be a very expensive solution,
それほど費用はかかりません
15:01
and it's got to work better than what we already have.
今ある仕組みより 上手くゆくはずです
15:05
So the question is, is there any hope for adoption of something like this,
問題は この装置が採用されるかどうかです
15:08
which would presumably save a lot of lives?
採用されれば 多くの命を救うことになります
15:13
And I think the answer, perhaps, lies in a story.
この答えとして ひとつお話しをしましょう
15:15
The answer both to why has a car seat been so successful,
チャイルドシートが成功している理由です
15:19
and why this may someday be adopted or not,
そしてこの装置が将来 採用されるかどうかは
15:23
lies in a story that my dad told me, relating to when he was a doctor
私の父が語った話にヒントがあります
15:26
in the U.S. Air Force in England. And this is a long time ago:
父は昔 在英の米空軍で医者をしていました
15:30
you were allowed to do things then you can't do today.
今では許されないことも 当時は可能でした
15:33
So, my father would have patients come in
病気とは言えないような症状の患者が
15:35
who he thought were not really sick.
来ることがあります
15:39
And he had a big jar full of placebo pills that he would give them,
そういう患者には
大きな瓶に入っている偽薬を取り出します
15:42
and he'd say, "Come back in a week, if you still feel lousy."
1週間しても良くならないなら もう一度来るように と言います
15:46
OK, and most of them would not come back,
ほとんどの患者は2度と来ませんでした
15:49
but some of them would come back.
しかし 中にはやって来る患者もあります
15:50
And when they came back, he, still convinced they were not sick,
彼等が病気では無いと確信している父は
15:52
had another jar of pills. In this jar were huge horse pills.
とても大きな錠剤が入った瓶を取り出します
15:56
They were almost impossible to swallow.
飲み込める大きさではありません
16:01
And these, to me, are the analogy for the car seats.
これがチャイルドシートの理論です
16:03
People would look at these and say, "Man, this thing is so big
患者はとても大きな薬だ と言います
16:07
and so hard to swallow. If this doesn't make me feel better,
この薬でも回復しないなら
16:11
you know, what possibly could?"
いったいどうしろと言うんだ?
16:13
And it turned out that most people wouldn't come back,
ほとんどの患者はもう戻ってくることはありませんでした
16:16
because it worked. But every once in a while,
薬が効いたからです
16:18
there was still a patient convinced that he was sick,
時には
自分が病気だと思っている患者がいるものです
16:21
and he'd come back. And my dad had a third jar of pills.
そういった患者には 第3の瓶を取り出します
16:26
And the jar of pills he had, he said,
父によれば
16:29
were the tiniest little pills he could find,
最小の錠剤で
16:31
so small you could barely see them.
その粒を見分けることができないくらいです
16:34
And he would say, listen, I know I gave you that huge pill,
この前の錠剤は巨大で
16:36
that complicated, hard-to-swallow pill before,
複雑で飲み込むのが難しかったはずだ
16:38
but now I've got one that's so potent,
今度の薬は良く効いて
16:42
that is really tiny and small and almost invisible.
目に見えないくらい小さな錠剤だ
16:44
It's almost like this thing here, which you can't even see."
見えないだろう
16:46
And it turned out that never,
そして 父が
16:49
in all the times my dad gave out this pill, the really tiny pill,
この小さな錠剤を与えた患者が
16:51
did anyone ever come back still complaining of sickness.
病状を訴えて再び来ることは
ありませんでした
16:54
So, my dad always took that as evidence
これは この小さな錠剤に
16:57
that this little, teeny, powerful pill
究極の偽薬効果があることの証拠だと
父は考えていました
17:00
had the ultimate placebo effect. And in some sense, if that's the right story,
それが正しい物語であれば
17:04
I think integrated car seats you will see, very quickly,
この一体型の座席は 短期間で
17:08
becoming something that everyone has. The other possible conclusion
普及すると思います
17:10
is, well, maybe after coming to my father three times,
父のもとを3度訪れて 偽薬を持ち帰った患者が
17:14
getting sent home with placebos, he still felt sick,
回復していないこともあり得ます
17:17
he went and found another doctor.
別の医者にかかった可能性もあります
17:19
And that's completely possible. And if that's the case,
そのようなケースがあり得るのであれば
17:21
then I think we're stuck with conventional car seats for a long time to come.
今後も長期にわたって
既存のチャイルドシートを使い続けることになるでしょう
17:23
Thank you very much.
ありがとうございました
17:26
(Applause)
(拍手)
17:27
(Audience: I just wanted to ask you, when we wear seatbelts
観客: シートベルトの着用は
17:31
we don't necessarily wear them just to prevent loss of life,
命を守る為だけではありません
17:33
it's also to prevent lots of serious injury.
重傷にならずにすみます
17:36
Your data looks at fatalities. It doesn't look at serious injury.
データは死亡率のみで重傷者数は含まれていません
17:38
Is there any data to show that child seats
チャイルド シートがシートベルトと同程度以下の効果しかないと
17:42
are actually less effective, or just as effective as seatbelts
示すデータはありますか?
17:44
for serious injury? Because that would prove your case.)
正当性を証明できると思います
17:47
Steven Levitt: Yeah, that's a great question. In my data, and in another data set
レヴィット: 私のデータでは
17:49
I've looked at for New Jersey crashes,
ニュージャージー州の衝突事故を調べました
17:52
I find very small differences in injury.
傷害についても 差異がほとんどありませんでした
17:55
So in this data, it's statistically insignificant differences
つまり チャイルド シートと3点式シートベルト着用での差異は
17:59
in injury between car seats and lap-and-shoulder belts.
統計的に重要ではありませんでした
18:01
In the New Jersey data, which is different,
ニュージャージー州のデータは
18:05
because it's not just fatal crashes,
死亡事故だけではありません
18:06
but all crashes in New Jersey that are reported,
報告のあった衝突事故も含んでいます
18:09
it turns out that there is a 10 percent difference in injuries,
傷害については10%の差異がありましたが
18:11
but generally they're the minor injuries.
そのほとんどは軽傷でした
18:14
Now, what's interesting, I should say this as a disclaimer,
念のために申し上げなければなりませんが
18:16
there is medical literature that is very difficult to resolve with this other data,
他のデータと相反する医療文献があり
18:18
which suggests that car seats are dramatically better.
チャイルドシートがはるかに優秀と解説しています
18:23
And they use a completely different methodology that involves --
彼等は 全く違った方法をとっています
18:27
after the crash occurs, they get from the insurance companies
衝突事故が起こった後に
18:29
the names of the people who were in the crash,
保険会社から
事故に関わった人の名前を聞き出しました
18:32
and they call them on the phone,
その人たちに電話をして
18:34
and they asked them what happened.
何が起きたのかを尋ねています
18:35
And I really can't resolve, yet,
まだ判断はつきかねることがあります
18:36
and I'd like to work with these medical researchers
こういった医学研究者の方々と共同で
18:39
to try to understand how there can be these differences,
差異が生じる原因を理解したいです
18:41
which are completely at odds with one another.
これは整合性がありません
18:44
But it's obviously a critical question.
この問題はよく考えなければなりません
18:47
The question is even if -- are there enough serious injuries
コストが見合うといえるほど多くの重傷が
18:50
to make these cost-effective? It's kind of tricky.
発生しているのでしょうか
18:53
Even if they're right, it's not so clear
彼等が正しかったとしても 十分に費用効果が高いかどうかは
18:56
that they're so cost-effective.
分からないのです
18:58
Translated by Kazuyuki Shimatani
Reviewed by Eriko T.

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About the Speaker:

Steven Levitt - Economist
Steven Levitt's eye-opening Freakonomics took economic theory into the real world of suburban parenting and urban drug gangs, turning conventional wisdom upside-down.

Why you should listen

With his 2005 book Freakonomics (co-authored with Stephen Dubner, a writer who profiled him for the New York Times), Steven Levitt carried hardcore economic method into the squishy real world and produced a pop-culture classic. Freakonomics is both an economics textbook and a series of cautionary tales about the fallacy of conventional wisdom. Levitt examines the links between real-world events, and finds many instances where the data simply doesn't back up popular belief.

He asks provocative questions: If selling crack is so lucrative, why do dealers live with their mothers? Does parental doting really improve children's test scores? Did New York City's crime rate really drop because of police tactics (or population trends)? His controversial answers stir debate, and sometimes backlash.

Read Steven Levitt's Reddit AMA >>

More profile about the speaker
Steven Levitt | Speaker | TED.com