Steven Levitt on child carseats

翻译人员: Xiaoqiao Xie 校对人员: Bill Hsiung

Once upon a time, there was a dread disease that afflicted children.

从前，有一个可怕的疾病。儿童能得这个病，

And in fact, among all the diseases that existed in this land,

事实上，在这个国家里所有儿童能够得的疾病中，

it was the worst. It killed the most children.

这个病杀伤力最大。绝大多数得病的儿童都死了。

And along came a brilliant inventor, a scientist,

后来出现了一位特别聪明的发明家，也是个科学家。

who came up with a partial cure for that disease.

他研究出了一种解决办法，能在一定程度上控制住这个疾病。

And it wasn't perfect. Many children still died,

但是这个办法不是十全十美的。很多儿童还是死去了。

but it was certainly better than what they had before.

但是用了这个办法，情况和从前比还是改善了很多。

And one of the good things about this cure was that it was free,

而且用这个方法的一个优点就是它差不多是免费的，

virtually free, and was very easy to use.

不光特便宜，还特别容易使用。

But the worst thing about it was that you couldn't use it

但是这个方法的最大的一个缺点是特别小的小孩子用不了，

on the youngest children, on infants, and on one-year-olds.

婴儿用不了，一岁的小孩子都用不了。

And so, as a consequence, a few years later,

所以几年后，

another scientist -- perhaps maybe this scientist

另一个科学家 —

not quite as brilliant as the one who had preceded him,

他可能没有像第一个科学家那么聪明，

but building on the invention of the first one --

但是他在第一个发明的基础上作了创新 —

came up with a second cure.

得出了第二个解决办法。

And the beauty of the second cure for this disease

这第二个针对这个疾病的治疗方案的好处在于，

was that it could be used on infants and one-year-olds.

它能用在婴儿和一岁大的小小孩身上。

And the problem with this cure was it was very expensive,

但这个治疗方案有个问题：它特别特别的贵。

and it was very complicated to use.

而且使用起来很复杂。

And although parents tried as hard as they could to use it properly,

虽然家长们用尽全力试图正确地使用这个方法，

almost all of them ended up using it wrong in the end.

绝大多数家长最终还是用错了。

But what they did, of course, since it was so complicated and expensive,

好在由于这个方法这么复杂这么贵，

they only used it on the zero-year-olds and the one-year-olds.

他们只用它来保护婴儿和一岁大的小孩子。

And they kept on using the existing cure that they had

等小孩子长到两岁，

on the two-year-olds and up.

家长们还是回去用老办法。

And this went on for quite some time. People were happy.

这种情况持续了很长一段时间。大家都挺满意的。

They had their two cures. Until a particular mother,

家长们就用这两个解决办法。直到有一天，有一个妈妈，

whose child had just turned two, died of this disease.

她的孩子刚过两周岁，死于这个疾病。

And she thought to herself, "My child just turned two,

她就想：“ 我的宝宝才刚两岁。

and until the child turned two, I had always used

直至今日，我一直用的是

this complicated, expensive cure, you know, this treatment.

那个复杂的贵的方法。

And then the child turned two, and I started using

然后我的宝宝两岁了，我就换成

the cheap and easy treatment, and I wonder" --

用那个便宜的，容易用的解决办法。如果（我没有换成那个便宜的方法）......”

and she wondered, like all parents who lose children wonder --

她不断地想着如果，就像其他所有那些失去了他们的宝宝的家长们一样，想着：

"if there isn't something that I could have done,

“如果我能为我的宝宝做什么（来救他一命），

like keep on using that complicated, expensive cure."

就是我应该继续用那个又复杂又贵的方法。”

And she told all the other people, and she said,

于是她奔走相告，她说：

"How could it possibly be that something

“ 便宜没好货！

that's cheap and simple works as well as something

看看这个这么便宜这么简单的解决办法，

that's complicated and expensive?"

它怎么可能跟那个那么复杂和昂贵的方法一样好呢？”

And the people thought, "You know, you're right.

于是大家都想：“ 嗯，言之有理。

It probably is the wrong thing to do to switch

我们换用便宜简单的办法，

and use the cheap and simple solution."

这没准是个错误。”

And the government, they heard her story and the other people,

于是政府也出来干预了。 他们听说了这个故事，也听了其他人的意见，

and they said, "Yeah, you're right, we should make a law.

政府说：“ 没错！你们都说得对。我们应该把这个（继续使用昂贵的治疗办法的）提案变成（人人必须遵守的）法律。

We should outlaw this cheap and simple treatment

我们必须把（对儿童）使用那个便宜又简单的治疗方案变成不合法的，

and not let anybody use this on their children."

不让任何人再用在他们的孩子身上了。”

And the people were happy. They were satisfied.

这下子大家都满意了，都高兴了。

For many years this went along, and everything was fine.

接下来很多很多年大家都这么做了，看起来万事大吉。

But then along came a lowly economist, who had children himself,

但是后来，一个不起眼的经济学家， 自己也有孩子的，跳出来了。

and he used the expensive and complicated treatment.

他用了这个又复杂又昂贵的方法，

But he knew about the cheap and simple one.

他也知道那个又便宜又简单的方法。

And he thought about it, and the expensive one

他想来想去，这个贵的办法怎么看

didn't seem that great to him. So he thought,

也不像是那么完美。所以他就想：

"I don't know anything about science, but I do know something about data,

“ 我不懂那些科学上的东西，但是我知道怎么看统计数据。

so maybe I should go and look at the data

说不定我应该去看看多年来的统计数据，

and see whether this expensive and complicated treatment

看看到底这个又复杂又昂贵的方法

actually works any better than the cheap and simple one."

是不是真的比那个又便宜又简单的方法好。”

And lo and behold, when he went through the data,

结果一看之下，当他翻遍了所有的数据

he found that it didn't look like the expensive, complicated

他发现这个又复杂又昂贵的方法

solution was any better than the cheap one,

并不比那个便宜的方法有效。

at least for the children who were two and older --

至少对于两岁和两岁以上的孩子 —

the cheap one still didn't work on the kids who were younger.

当然这个便宜的方法两岁以下的还是不能用。（所以也没法比。）

And so, he went forth to the people and he said,

所以他就跳出来和大家说：

"I've made this wonderful finding:

“ 我有个了不得的发现。

it looks as if we could just use the cheap and simple solution,

原来（对两岁和两岁以上的儿童）我们可以就用这个便宜简单的方法，

and by doing so we could save ourselves 300 million dollars a year,

同时一年我们还可以省下三亿美元。

and we could spend that on our children in other ways."

用这些钱我们可以为我们的孩子们做更多的事。”

And the parents were very unhappy, and they said,

结果家长们都不高兴了，他们说：

"This is a terrible thing, because how can the cheap and easy thing

“ 这真是耸人听闻！这个便宜简单的方法

be as good as the hard thing?" And the government was very upset.

怎么可能和那个复杂的方法媲美呢？”

And in particular, the people who made this expensive solution

接下来政府也生气了，尤其是那些靠这个贵的方法挣钱的人们

were very upset because they thought,

特别生气。因为他们想：

"How can we hope to compete with something that's essentially free?

“ 我们怎么可能和一个基本上是免费的方法竞争呢？

We would lose all of our market."

我们肯定会全失去整个市场。”

And people were very angry, and they called him horrible names.

这样大家都愤怒了，他们称这个经济学家坏人，

And he decided that maybe he should leave the country

他想说不定他应该离开这个国家几天，

for a few days, and seek out some more intelligent,

去一个叫牛津的地方，

open-minded people in a place called Oxford,

去找其他一些更聪明更开明的人谈谈，

and come and try and tell the story at that place.

看看他们能不能听进这个故事。

And so, anyway, here I am. It's not a fairy tale.

所以，我来到了这里。这不是个童话故事，

It's a true story about the United States today,

这是在美国真实发生的事。

and the disease I'm referring to is actually

我说的这个疾病其实

motor vehicle accidents for children.

是车祸，发生在儿童身上的车祸。

And the free cure is adult seatbelts, and the expensive cure --

这个免费的治疗方案是用成人用的安全带，而这个贵的治疗方案 —

the 300-million-dollar-a-year cure -- is child car seats.

这个三亿美元一年的治疗方案 — 是儿童汽车安全座椅。

And what I'd like to talk to you about today

我今天想给你们看看

is some of the evidence why I believe this to be true:

一些证据来支持我认为正确的观点：

that for children two years old and up,

那就是对于两岁和两岁以上的孩子，

there really is no real benefit -- proven benefit -- of car seats,

安全汽车座椅其实没有什么用，没有证据显示有用。

in spite of the incredible energy

尽管大多数人竭尽全力

that has been devoted toward expanding the laws

试图推广使用安全座椅的法律，

and making it socially unacceptable

试图推广让孩子只用安全带是错的这个观点。

to put your children into seatbelts. And then talk about why --

然后我会谈到为什么，

what is it that makes that true?

为什么人们死心塌地地相信这个错误观点？

And then, finally talk a little bit about a third way,

最后，我希望和你们介绍一个（在车祸中保护儿童的）新方法。

about another technology, which is probably better than anything we have,

这个新技术很可能比我们有的这两个方法都好，

but which -- there hasn't been any enthusiasm for adoption

但是人们还不是太有热情去用。

precisely because people are so enamored

那是因为人们对于汽车安全座椅这个主意

with the current car seat solution. OK.

还是特别迷恋。好的。

So, many times when you try to do research on data,

多数情况下当你试图研究统计数据时，

it records complicated stories -- it's hard to find in the data.

这些数据包含了十分复杂的背景故事。想要发现你要找的东西是很困难的 —

It doesn't turn out to be the case when you look at seatbelts versus car seats.

好在当你比较安全带和儿童汽车座椅时没这个问题。

So the United States keeps a data set

美国政府保存了一份数据

of every fatal accident that's happened since 1975.

包含了 1975 年以来每起车祸死亡的案子。

So in every car crash in which at least one person dies,

也就是说（1975 年以来）每起车祸，只要有一个人死亡，

they have information on all of the people.

他们就记录下所有车祸中涉及到的人的信息。

So if you look at that data -- it's right up on the National Highway

所以当你研究这些数据时 — 这些数据就在

Transportation Safety Administration's website --

国家高速交通系统安全局的网页上。

you can just look at the raw data,

你可以通过看这些原始数据，

and begin to get a sense of the limited amount of evidence

发现对于两岁以上的儿童，支持儿童汽车座椅（比安全带好）

that's in favor of car seats for children aged two and up.

的证据是非常少的。

So, here is the data. Here I have, among two- to six-year-olds --

这就是统计数据。这里显示两岁到六岁的儿童 —

anyone above six, basically no one uses car seats,

当孩子六岁后他们就不用安全座椅了，所以没的可比 —

so you can't compare -- 29.3 percent of the children who are unrestrained

当车祸中有至少一个人死亡时，如果没有用任何保护措施，

in a crash in which at least one person dies, themselves die.

这些车祸中的儿童死亡率是 29.3%。

If you put a child in a car seat, 18.2 percent of the children die.

如果孩子坐在汽车安全座椅里，死亡率是 18.2%。

If they're wearing a lap-and-shoulder belt, in this raw data,

如果孩子戴了腰上和肩膀上的安全带， 在这份原始数据中，

19.4 percent die. And interestingly, wearing a lap-only seatbelt,

死亡率是 19.4%。 有趣的是，使用仅仅是腰部的安全带，

16.7 percent die. And actually, the theory tells you

死亡率只有 16.7%。 实际上，原则上来讲

that the lap-only seatbelt's got to be worse

腰部安全带应该比腰部和肩部都有保护的安全带效果差。

than the lap-and-shoulder belt. And that just reminds you

这个数据提醒了我们

that when you deal with raw data, there are hundreds

当我们看真实的原始数据时，

of confounding variables that may be getting in the way.

需要考量成百上千的因素，它们都有可能影响最后的结果。

So what we do in the study is -- and this is just presenting

所以我们换了个角度来看，

the same information, but turned into a figure to make it easier.

我们还是用这些数据，但是作成图表所以看起来方便些。

So the yellow bar represents car seats,

这些黄色的条带代表使用汽车安全座椅的（儿童的死亡率），

the orange bar lap-and-shoulder, and the red bar lap-only seatbelts.

橙色的条带代表使用腰肩安全带的（儿童的死亡率）， 红色的条带代表了使用腰部安全带的（儿童的死亡率）。

And this is all relative to unrestrained --

这些条带都已经和没用任何保护措施的（儿童的死亡率）取过比例了。

the bigger the bar, the better. Okay.

条带越高越好。

So, this is the data I just showed, OK?

所以这（左边的图）就是我刚才给你们看的数据。

So the highest bar is what you're striving to beat.

这条最高的条带，就是大家拼命不承认的。

So you can control for the basic things, like how hard the crash was,

如果我们（在这个研究中）考量所有基本的因素，比如这个车祸本身有多严重，

what seat the child was sitting in, etc., the age of the child.

车里的孩子坐在哪个位置上，等等，还有孩子的实际年龄，

And that's that middle set of bars.

那么结论就是中间这组条带。

And so, you can see that the lap-only seatbelts

你可以看到腰部安全带

start to look worse once you do that.

开始看起来不如（原始数据里显示的）安全了。

And then finally, the last set of bars,

最后，最右边的这组条带，

which are really controlling for everything

是在我们真正考虑了所有可能的影响因素之后的结论。

you could possibly imagine about the crash,

你可以想象不同的车祸，

50, 75, 100 different characteristics of the crash.

五十种，七十五种，一百种不同的车祸，

And what you find is that the car seats and the lap-and-shoulder belts,

而最后你发现使用汽车安全座椅和使用腰肩安全带，

when it comes to saving lives, fatalities look exactly identical.

当我们比较谁能救命时，平均的死亡率是完全一样的。

And the standard error bands are relatively small around these estimates as well.

同时死亡率的分散程度都很小。

And it's not just overall. It's very robust

而且还不是仅仅对所有的车祸都是这样，

to anything you want to look at.

当你比较任何一种类型车祸，这个结论都适用。

One thing that's interesting: if you look at frontal-impact crashes --

有个现象很有趣：当你比较那些撞车头的车祸 —

when the car crashes, the front hits into something --

也就是当车祸发生时，是车头撞上了任何别的东西 —

indeed, what you see is that the car seats look a little bit better.

汽车安全座椅实际上还是稍微好些。

And I think this isn't just chance.

而我觉得这必有原因。

In order to have the car seat approved,

原因就是为了能够得到许可生产一种汽车安全座椅，

you need to pass certain federal standards,

你需要达到一些国家定的标准，

all of which involve slamming your car into a direct frontal crash.

在测试的时候，假想的车祸都是直接撞车头的。

But when you look at other types of crashes, like rear-impact crashes,

但是当你看其它种类的车祸的时候，比如车后面被撞了，

indeed, the car seats don't perform as well.

汽车座椅就不是那么有用了。

And I think that's because they've been optimized to pass,

我认为这是因为它们都是针对撞车头的测试来设计的，

as we always expect people to do,

就像大家通常会做的，

to optimize relative to bright-line rules

针对明文规定的政策来准备对策，

about how affected the car will be.

对车辆安全的问题也是一样。

And the other thing you might argue is,

你还可以提出另一个观点：

"Well, car seats have got a lot better over time.

汽车座椅应该会变得越来越安全。

And so if we look at recent crashes --

如果我们看最近发生的车祸数据 —

the whole data set is almost 30 years' worth of data --

这里整个的数据是过去三十年的 —

you won't see it in the recent crashes. The new car seats are far, far better."

你应该会发现新数据显示汽车座椅更安全。新的汽车安全座椅比旧的设计好得多了。

But indeed, in recent crashes the lap-and-shoulder seatbelts,

但是事实上，最新的数据显示腰肩安全带

actually, are doing even better than the car seats.

事实上比汽车安全座椅更好。

They say, "Well, that's impossible, that can't be."

人们会说：“ 这不可能，这不合理。”

And the line of argument, if you ask parents, is,

如果你问家长们，他们的观点是：

"But car seats are so expensive and complicated,

“ 汽车座椅那么贵，那么复杂，

and they have this big tangle of latches,

它们有一大团这样那样的搭扣。

how could they possibly not work better than seatbelts

它们怎么可能会不如安全带有用呢？

because they are so expensive and complicated?"

它们是这么贵这么复杂！”

It's kind of an interesting logic,

这是个挺有趣的逻辑。

I think, that people use. And the other logic, they say,

我想一般人都会相信。另一个逻辑家长们用的，是：

"Well, the government wouldn't have told us [to] use them

“ 如果安全带更安全的话，

if they weren't much better."

政府不会无缘无故地就不让我们给孩子用的。”

But what's interesting is the government telling us to use them

但讽刺的是政府让我们用安全座椅，

is not actually based on very much.

实际上是有点无缘无故的。

It really is based on some impassioned pleas of parents

这真是本着某些激动的家长的苦苦恳求。

whose children died after they turned two,

他们的孩子长过了两岁，之后在车祸中过世了。

which has led to the passage of all these laws -- not very much on data.

他们的恳求使得政府通过了这些法律，并不是通过真的研究得出的结论。

So you can only get so far, I think, in telling your story

通过看这些抽象的统计数据， 我想我只能

by using these abstract statistics.

证明这么多。

And so I had some friends over to dinner, and I was asking --

所以当我的朋友们来家里吃晚饭时 —

we had a cookout -- I was asking them what advice they might have for me

我们有一次露天烧烤的时候 — 我问他们的意见，我该怎么做来进一步证明我的推论。

about proving my point. They said, "Why don't you run some crash tests?"

他们说：“ 你为什么不自己做些碰撞测试呢？”

And I said, "That's a great idea."

我说：“ 这是个好主意。”

So we actually tried to commission some crash tests.

所以我们试着委托人做些碰撞测试。

And it turns out that as we called around to the independent

结果我们给国内那些作汽车碰撞测试的机构

crash test companies around the country,

打了一圈电话，

none of them wanted to do our crash test

没有一个愿意替我们做测试的。

because they said, some explicitly, some not so explicitly,

他们说 — 有些是明白说的，有些是含含糊糊说的 —

"All of our business comes from car seat manufacturers.

“ 我们的生意都是来自那些生产汽车安全座椅的商家的。

We can't risk alienating them by testing seatbelts relative to car seats."

我们不能冒着得罪他们的风险，（为你）测试安全带和安全座椅比（哪个更好）。”

Now, eventually, one did. Under the conditions of anonymity,

直至今日，最终一家机构，还是帮了我们一把。他们说只要是匿名的，

they said they would be happy to do this test for us --

他们乐意替我们做这个测试。

so anonymity, and 1,500 dollars per seat that we crashed.

所以（条件是）不能透露他们的名字，而且每个撞毁的车座椅我们得付一千五百美元，

And so, we went to Buffalo, New York,

我们去纽约州的水牛城（做了这个测试）。

and here is the precursor to it.

这里就是我们的先锋部队了，

These are the crash test dummies,

这些是用来做测试的假人，

waiting for their chance to take the center stage.

排队等着上台。

And then, here's how the crash test works.

这里你看到的是我们怎么做这些测试。

Here, they don't actually crash the entire car, you know --

这里，他们并不真的撞坏整辆汽车，要知道 —

it's not worth ruining a whole car to do it.

为这类测试撞毁整辆车不值得。

So they just have these bench seats,

所以他们用的是这些双人长座椅，

and they strap the car seat and the seatbelt onto it.

然后把汽车座椅或者安全带装在这些座椅上。

So I just wanted you to look at this.

我想让你看看这个图像，

And I think this gives you a good idea of why parents think

我想着给你一个很好的理由为什么家长们觉得

car seats are so great. Look at the kid in the car seat.

汽车安全座椅好。看看这个（假）孩子，坐在汽车安全座椅中，

Does he not look content, ready to go,

难道他看起来不是舒舒服服，整装待发么？

like he could survive anything? And then, if you look at the kid in back,

难道他看起来不是什么天灾人祸都能挺过去么？然后你再看看这个坐在后排的（仅仅用了安全带的假）孩子，

it looks like he's already choking before the crash even happens.

看起来他已经（被安全带勒的）喘不过来气了，更别提发生车祸了。

It's hard to believe, when you look at this, that

当你看这段碰撞测试录像的时候，令人难以置信的是，

that kid in back is going to do very well when you get in a crash.

坐在后排的（只用了安全带的假）孩子安然无恙。

So this is going to be a crash

碰撞发生的时候，

where they're going to slam this thing forward into a wall

这整个装置会被使劲摔到前面的墙上，

at 30 miles an hour, and see what happens. OK?

速度是三十英里每小时（四十八公里每小时），然后我们看发生了什么。

So, let me show you what happens.

这里请允许我展示给你们看发生了什么。

These are three-year-old dummies, by the way.

对了，这两个是模拟三岁大的孩子的假人，

So here -- this is the car seat. Now watch two things:

— 这里是（坐在）安全座椅（里的孩子）。现在注意两件事，

watch how the head goes forward,

注意假人的头部向前猛冲，

and basically hits the knees -- and this is in the car seat --

基本上撞在他自己的膝盖上。这是发生在孩子坐在汽车安全座椅里的情况。

and watch how the car seat flies around, in the rebound, up in the air.

第二是注意在反弹的时候，汽车座椅整个飞起来，飞在空中，

The car seat's moving all over the place.

整个汽车座椅飞来飞去。

Bear in mind there are two things about this.

请记住在这个汽车安全座椅测试中有两个关键：

This is a car seat that was installed by someone

一个是这个汽车座椅是由一个会装汽车座椅的人装上的，

who has installed 1,000 car seats, who knew exactly how to do it.

他已经装了超过一千个汽车座椅了。

And also it turned out these bench seats

而且这个座椅是装在双人长椅上。

are the very best way to install car seats.

双人长椅是最适合装汽车座椅的，

Having a flat back makes it much easier to install them.

因为这种椅子的后背是平的，汽车座椅容易装牢固。

And so this is a test that's very much rigged in favor of the car seat,

所以说这个测试其实是偏帮着汽车安全座椅的。

OK? So, that kid in this crash fared very well.

同意吧？所以这个汽车座椅中的假孩子的结果不错，

The federal standards are

按照国家标准

that you have to score below a 1,000

这类碰撞测试你得得到危险系数少于一千，

to be an approved car seat on this crash,

才能得到执照生产这个汽车安全座椅。

in some metric of units which are not important.

这里就不介绍危险系数是怎么评的了。

And this crash would have been about a 450.

这个汽车座椅的得分是 450。

So this car seat was actually an above-average car seat

从消费者评分来看，

from Consumer Reports, and did quite well.

这个汽车座椅其实高于一般水平，所以也表现很好。

So the next one. Now, this is the kid, same crash,

接下来，现在我们看到的是这个用安全带的假孩子，同样的测试，

who is in the seatbelt. He hardly moves at all, actually,

他其实几乎没怎么飞起来，

relative to the other child. The funny thing is,

尤其是和那个坐在汽车安全座椅中的假孩子比。有趣的是，

the cam work is terrible because they've only set it up

这个摄像机的效果很差，因为摄像机是他们为了给安全座椅们录像而装的，

to do the car seats, and so, they actually don't even have a way

所以根本没法把摄像机挪到后边

to move the camera so you can see the kid that's on the rebound.

你也就看不到反弹的时候这个假孩子的情况。

Anyway, it turns out that those two crashes, that actually

总而言之，在这两起碰撞测试中，

the three-year-old did slightly worse. So, he gets about a 500

这个用安全带的三岁大的假人表现稍差，得分是 500，

out of -- you know, on this range -- relative to a 400 and something.

一般的范围是 400 到 1000。

But still, if you just took that data from that crash

但是如果你单把 500 这个危险系数，

to the federal government, and said, "I have invented a new car seat.

给政府看，跟他们说：“ 我设计了一个新的汽车安全座椅，（危险系数是500。）

I would like you to approve it for selling,"

我希望你能批准我销售这个座椅。”

then they would say, "This is a fantastic new car seat, it works great.

他们会说：“ 这个汽车座椅非常好，表现很好。”

It only got a 500, it could have gotten as high up as a 1,000."

（因为）它的危险系数才 500， 比 1000 少就够了。

And this seatbelt would have passed with flying colors

所以说这个安全带可以被当作汽车安全座椅一样批准使用，

into being approved as a car seat.

毫无问题。

So, in some sense, what this is suggesting

所以一定程度上，这个事实告诉我们，

is that it's not just that people are setting up their car seats wrong,

并不是大家装汽车座椅的时候装错了，

which is putting children at risk. It's just that, fundamentally,

让孩子冒风险。根本是

the car seats aren't doing much.

安全座椅并不更安全。

So here's the crash. So these are timed at the same time,

这里是另一个碰撞测试，全发生在同一时刻。

so you can see that it takes much longer with the car seat --

你可以看到汽车座椅费了长的多的时间回到原位 —

at rebound, it takes a lot longer --

在反弹的时候汽车座椅需要长的多的时间（恢复原位）。

but there's just a lot less movement for child who's in the seatbelt.

另外使用安全带的假孩子移动得少的多。

So, I'll show you the six-year-old crashes as well.

我再给你们看一个用模拟六岁大的孩子的假人作的测试。

The six-year-old is in a car seat, and it turns out

这个假装是六岁大的孩子坐在汽车安全座椅中，结果 —

that looks terrible, but that's great. That's like a 400, OK?

看起来真恐怖，但是数据其实不错，400 分。

So that kid would do fine in the crash.

所以他可以没事。

Nothing about that would have been problematic to the child at all.

没有什么问题会发生在他身上。

And then here's the six-year-old in the seatbelt,

这里是假装六岁大的假人用了安全带，

and in fact, they get exactly within, you know,

事实上他们两个得到了几乎完全一样的分数，

within one or two points of the same. So really, for the six-year-old,

只差了一两分。所以说对于六岁大的孩子，

the car seat did absolutely nothing whatsoever.

汽车安全座椅一点作用都没有。

That's some more evidence, so in some sense --

这里是更多的数据。所以在很大程度上 —

I was criticized by a scientist, who said, "You could never publish

我曾被一个科学家批评说：“ 就凭着四个例子，你永远也不可能

a study with an n of 4," meaning those four crashes.

发表你的研究结果。” 指的是我只做了四次的碰撞实验。

So I wrote him back and I said, "What about an n of 45,004?"

所以我写信回复他，我说：“ 如果我有四万五千零四个例子，那又怎么样？”

Because I had the other 45,000 other real-world crashes.

因为我有另外四万五千个实际发生的车祸例子。

And I just think that it's interesting that the idea

我只是觉得，（这个研究手段的差异）很有趣：

of using real-world crashes, which is very much something

使用真实事例，

that economists think would be the right thing to do,

对于经济学家来说是理所当然的，

is something that scientists don't actually, usually think --

却是科学研究工作者们选择不去做的 —

they would rather use a laboratory,

科学家们宁愿作实验，

a very imperfect science of looking at the dummies,

用问题百出的实验科学，就像我们使用假人做研究，

than actually 30 years of data of what we've seen

而不用三十年来我们看到的，

with children and with car seats.

关于儿童（安全）和汽车安全座椅（的表现）的真实数据。

And so I think the answer to this puzzle

所以我认为这个谜团的答案，

is that there's a much better solution out there,

其实是已经存在的另一个更好的解决办法，

that's gotten nobody excited because everyone

只是没人感兴趣，因为每个人都

is so delighted with the way car seats are presumably working.

还是对汽车安全座椅的所谓表现挺满意。

And if you think from a design perspective,

如果你从头设计，

about going back to square one, and say,

回到一片空白的阶段，

"I just want to protect kids in the back seat."

“ 你只是想要保护后座上的孩子”。

I don't there's anyone in this room who'd say,

我不认为在座的诸位会说：

"Well, the right way to start would be,

“ 好的，我们应该这么做，

let's make a great seat belt for adults.

让我们给成人设计特别安全的安全带，

And then, let's make this really big contraption

然后让我们拿一些链子拼凑一下，

that you have to rig up to it in this daisy chain."

就给孩子用这个奇形怪状的装置。”

I mean, why not start -- who's sitting in the back seat anyway except for kids?

我的意思是，为什么不从这个角度开始想 — 怎么保护后座上坐的人，如果这个人不是个孩子？

But essentially, do something like this,

基本上，我们会这么做，

which I don't know exactly how much it would cost to do,

我并不知道这个装置会有多贵，

but there's no reason I could see

但是我不认为

why this should be much more expensive than a regular car seat.

这个会比一个普通的汽车安全座椅更贵多少。

It's just actually -- you see, this is folding up -- it's behind the seat.

这个基本上是一个 — 你可以看到，这个可以折叠起来 — 翻到后座里去。

You've got a regular seat for adults, and then you fold it down,

平时这就是一个正常的后座，成人能用的，一翻下来，

and the kid sits on top, and it's integrated.

孩子们就可以坐在它上面。这个装置是可以装在车里的。

It seems to me that this can't be a very expensive solution,

我认为这不会是个很昂贵的办法，

and it's got to work better than what we already have.

而且这个办法应该比我们现有的方法好的多。

So the question is, is there any hope for adoption of something like this,

现在的问题变成，到底有没有希望，来开始使用这样的一个东西，

which would presumably save a lot of lives?

一个可能能救很多条性命的东西？

And I think the answer, perhaps, lies in a story.

我想，答案尽在下面这个故事里。

The answer both to why has a car seat been so successful,

这个答案可以解释为什么汽车安全座椅那么成功，

and why this may someday be adopted or not,

也可以解释为什么我的新发明可能某一天会被应用，当然也可能不会。

lies in a story that my dad told me, relating to when he was a doctor

这个答案包含在下面这个我爸爸讲给我听的故事里，当是他是一个大夫，

in the U.S. Air Force in England. And this is a long time ago:

在英国的美国空军驻地工作。这是很久以前的事了。

you were allowed to do things then you can't do today.

那时候（作为一个大夫），你还可以有很多自主权。

So, my father would have patients come in

有的病人来找我爸爸治疗，

who he thought were not really sick.

但是我爸爸诊断出他们没病。

And he had a big jar full of placebo pills that he would give them,

他有一大罐安慰药片，他可以给这些病人，

and he'd say, "Come back in a week, if you still feel lousy."

他会说：“ 要是吃了药一周后还不舒服，再来找我。”

OK, and most of them would not come back,

绝大部分的病人不会再来。

but some of them would come back.

当然有一部分还是会回来找他，

And when they came back, he, still convinced they were not sick,

他如果还是觉得这些人没病，

had another jar of pills. In this jar were huge horse pills.

他就会使用另一罐安慰药片。这罐药都是特别大片的药

They were almost impossible to swallow.

它们大到没法吞咽。

And these, to me, are the analogy for the car seats.

这些药片对我来说就像是汽车安全座椅。

People would look at these and say, "Man, this thing is so big

人们看到它们，自然而然地会说：“ 天啊，这东西这么大，

and so hard to swallow. If this doesn't make me feel better,

这么难以下咽，如果这个还治不好我的病，

you know, what possibly could?"

你想想，那没什么药能了。”

And it turned out that most people wouldn't come back,

结果绝大部分回来的病人都没再来找。

because it worked. But every once in a while,

因为这次大药片起了安慰作用。但是时不时地，

there was still a patient convinced that he was sick,

还是会有一个病人第三次回来，觉得他还是有病，

and he'd come back. And my dad had a third jar of pills.

这次我爸爸就会拿出他的第三个药罐。

And the jar of pills he had, he said,

这罐药，他告诉我，

were the tiniest little pills he could find,

是他能找到的最小的安慰药片，

so small you could barely see them.

小到你几乎看不清它们。

And he would say, listen, I know I gave you that huge pill,

他会对病人说，你看，我知道我上次给了你那些大药片，

that complicated, hard-to-swallow pill before,

那些看起来挺高深的，难以下咽的药片（结果没用）。

but now I've got one that's so potent,

但是这次，我得到了这些特别强效的药片，

that is really tiny and small and almost invisible.

它们特别小，你几乎看不见，

It's almost like this thing here, which you can't even see."

（就像我给你们看的我的发明一样，你一般都注意不到。）”

And it turned out that never,

结果再也没有人回头来找他。

in all the times my dad gave out this pill, the really tiny pill,

每次我爸爸给出这第三种药片，这种小药片，

did anyone ever come back still complaining of sickness.

再没有人回头来找他说他们有病了。

So, my dad always took that as evidence

所以我爸爸总是拿这个说嘴，

that this little, teeny, powerful pill

说这种小小的强力药片

had the ultimate placebo effect. And in some sense, if that's the right story,

反而有最强的安慰剂的效果。某种程度上，如果我爸爸的故事真的说明问题，

I think integrated car seats you will see, very quickly,

我认为你也会开始看到这种内置的安全座椅，很快地

becoming something that everyone has. The other possible conclusion

变成人手一件的东西。当然另一个可能性是

is, well, maybe after coming to my father three times,

这些病人来找了我爸爸三趟，三趟都拿了安慰剂回去，

getting sent home with placebos, he still felt sick,

还是觉得不舒服，

he went and found another doctor.

他就去找别的大夫了。

And that's completely possible. And if that's the case,

这是有可能的。如果这个可能性是真的，

then I think we're stuck with conventional car seats for a long time to come.

我想我们在接下来很长一段时间里，只好继续用传统的汽车安全座椅。

Thank you very much.

谢谢大家。

(Applause)

（掌声）

(Audience: I just wanted to ask you, when we wear seatbelts

（听众发问：我只想问一个问题，当我们使用安全带时

we don't necessarily wear them just to prevent loss of life,

我们不光是为了防止车祸造成的死亡，

it's also to prevent lots of serious injury.

也是为了防止车祸造成的受伤。

Your data looks at fatalities. It doesn't look at serious injury.

你研究了死亡率，但是没有研究受重伤的可能性。

Is there any data to show that child seats

有没有任何数据是表明儿童汽车安全座椅在防止受伤这方面

are actually less effective, or just as effective as seatbelts

比安全带效果差，或者至少不比安全带好的？

for serious injury? Because that would prove your case.)

因为这会加强你的论据。）

Steven Levitt: Yeah, that's a great question. In my data, and in another data set

是的，这是个好问题。在我的数据里，另一组数据里，

I've looked at for New Jersey crashes,

我调查了新泽西州的车祸案例。

I find very small differences in injury.

两种防范措施在减少受伤这方面差异很小。

So in this data, it's statistically insignificant differences

在今天大家看到的这组数据中，使用安全座椅和使用安全带之间，在减少受伤这方面，

in injury between car seats and lap-and-shoulder belts.

统计上来看没有任何显著差异。

In the New Jersey data, which is different,

在新泽西州的统计数据中，不同的数据，

because it's not just fatal crashes,

因为我们看到的不仅仅是致命的车祸。

but all crashes in New Jersey that are reported,

而在新泽西州的所有车祸。

it turns out that there is a 10 percent difference in injuries,

结果表明两种防范措施有一成的差别，

but generally they're the minor injuries.

但是总的来说这些车祸造成的都是小伤。

Now, what's interesting, I should say this as a disclaimer,

有趣的是，我得说，尽管我不认同，

there is medical literature that is very difficult to resolve with this other data,

有篇医学论文用新泽州的数据很难解释，

which suggests that car seats are dramatically better.

这篇医学论文说汽车安全座椅的安全性要好得多（比一成多）。

And they use a completely different methodology that involves --

这篇论文用了非常不同的实验手段，包括 —

after the crash occurs, they get from the insurance companies

在车祸发生后，他们从保险公司那里得到了

the names of the people who were in the crash,

车祸中牵连的人的名字，

and they call them on the phone,

他们给这些人打了电话，

and they asked them what happened.

详细问了事情发生的经过。

And I really can't resolve, yet,

我实在是解释不了。

and I'd like to work with these medical researchers

我希望能有机会和这些医学工作者一起工作，

to try to understand how there can be these differences,

来弄明白为什么（我们的结果）会有那么大的差异，

which are completely at odds with one another.

会有这些天差地别的结果。

But it's obviously a critical question.

但这（个受伤率的议题）明显是个关键的问题。

The question is even if -- are there enough serious injuries

这个问题就是，即使（汽车安全座椅稍好一点）—，我们有没有那么多车祸受伤的情况，

to make these cost-effective? It's kind of tricky.

使得我们的花费值回票价？这是个难以判断的问题。

Even if they're right, it's not so clear

即使这些人的结果是对的，我们还是不清楚

that they're so cost-effective.

这些汽车安全座椅是不是值得。