PBS高端访谈:经济流动性与不平等性的起伏变化

 　　JUDY WOODRUFF: Our next segment examines new research that's drawing attention for its findings about economic opportunity in America.

　　Jeffrey Brown picks it up from here.

　　JEFFREY BROWN: Is it still possible to climb to the top in America? In a paper released this week, a group of economists¹ found the prospects² for upward mobility³, the theme of the American dream, haven't changed in the last several decades.

　　The ability to move up the income ladder hasn't worsened, but it also hasn't improved.

　　Raj Chetty, one of the authors of the study, is professor of economics at Harvard University, and he joins me now.

　　Well, thanks for joining us.

　　It might be helpful first to define what you mean by upward mobility.

　　RAJ CHETTY, Harvard University: Sure.

　　What we mean by upward mobility in this study is a child's chances of moving up in the income distribution. One way to measure that is the chance that a child, say, from the bottom fifth of the income distribution reaches the top fifth of the income distribution.

　　You could also measure it in other ways. What is the average outcome of children from low-income families or what are their odds⁴ of reaching the middle class? No matter which way we define upward mobility, the main finding of our most recent study is that your odds of climbing up the income ladder haven't changed significantly over the past three decades or so.

　　JEFFREY BROWN: So were you surprised by that finding?

　　RAJ CHETTY: Yes, we were quite surprised, because I think many Americans have the perception, and certainly the public conversation has been that prospects for upward mobility are declining in the U.S.

　　And, to the contrary, what we found is that your odds of climbing up the income ladder haven't actually changed significantly, even while the amount of inequality, as has been widely discussed, has increased substantially over this period.

　　JEFFREY BROWN: Well, so let's go to that.

　　I mean, first of all, is it a glass half-full or half-empty situation? How do you look at the problem that we have today?

　　RAJ CHETTY: Well, I think you shouldn't interpret the lack of a decline in upward mobility as good news, in the sense that intergenerational mobility in the U.S., social mobility, is lower than virtually any other developed country for which we currently have data.

　　And so the way to think about this is that upward mobility is quite low, unfortunately, on average in the U.S., and it has remained -- it's been persistently⁶ low for the past few decades. And so, in that sense, I think it's still an important and urgent policy priority to focus on identifying ways of improving upward mobility.

　　JEFFREY BROWN: Well, in thinking about that, about possible policy prescriptions⁷, how much do we know about why this has happened, why it has stayed the same or stagnated⁸?

　　RAJ CHETTY: Yes, that's a challenging question.

　　One of the trends that we have seen, as I just mentioned, is that inequality has increased. And conventional wisdom is that greater inequality might make upward mobility more difficult. One way to picture that is think of the income distribution as a ladder, and the rungs of the ladder or the percentiles of the income distribution, while inequality has been increasing, that means the rungs of the ladder have grown further apart.

　　And so you might have thought, intuitively, that's going to make it harder for kids to climb up that ladder if they are starting from a low position. That turns out not to have happened. And so perhaps one hypothesis that other things have changed at the same time. Over the past several decades, we have had significant improvements in civil rights, expanded access to higher education, and a number of other anti-poverty efforts that might have offset⁹ that detrimental¹⁰ effects of other forces in the economy.

　　JEFFREY BROWN: But, as you said, inequality certainly has increased. So, what -- make the connection here for us. I saw a quote where you said, "Now it matters more who your parents are today than it did in the past."

　　So you're saying that the consequences of inequality have increased, somehow impacting mobility, upward mobility?

　　RAJ CHETTY: That's exactly right, Jeff.

　　So, the way to think about that is because the rungs of the ladder are further apart, to go back to the analogy I was just using, who your parents are, if you happen to be by chance born to parents at the bottom of that ladder vs. the top of the ladder, that is more consequential¹¹ today than it was in the past, precisely¹² because the ladder is now expanded.

　　So if you are born to parents who happen to be at the 20th percentile, instead of the 80th percentile, that is a much bigger gap today than it was 30 or 40 years ago. And so the consequences of the fact that we have relatively¹³ low levels of mobility in the U.S. are much more serious today than they were in the past. And so we should be more concerned about the fact that mobility is quite low today.

　　JEFFREY BROWN: I want to come back to one other thing you mentioned, which is the comparison to other countries.

　　You said because the U.S. remains¹⁴ behind many other countries now when it comes to upward mobility. Do we know why? Do we know what other countries are doing that make it easier for mobility?

　　RAJ CHETTY: Well, it's difficult to draw lessons from cross-country comparisons, because there are lots of other differences across areas.

　　But in another study we have done, which we actually discussed on the NewsHour a few months ago...

　　JEFFREY BROWN: I remember, yes.

　　RAJ CHETTY: ... we look at the geography of mobility within the United States, and show that there is a lot of variation in upward mobility across areas within the U.S.

　　So, to give you one example, the odds of a child from the bottom 20 percent reaching the top 20 percent are four out of 100 in Atlanta, but 13 out of 100 in San Jose, nearly three times as large. And so the question that we ask is, what is driving that difference in upward mobility within the U.S.?

　　And we identify a set of factors, a set of correlated factors, such as segregation¹⁵, income inequality, the quality of schools in an area, family structure and measures of social cohesiveness¹⁶, all of which are related to higher levels of upward mobility.

　　Now, we don't know exactly what the causal determinants are, what the recipe is that makes San Jose have higher upward mobility than Atlanta. But that's exactly what we would like to figure out and identify policies to improve upward mobility going forward.

　　JEFFREY BROWN: Well, and do you and your colleagues look at other kind of policy areas, I'm thinking about -- where -- that could make a difference, I mean, in upward mobility? I am thinking about education, for example, whether it's public K through 12 or higher education.

　　RAJ CHETTY: Absolutely.

　　I think education could play a key role here. And we have done other work showing that the quality of teaching, in particular in elementary schools, has very significant impacts on kids' outcomes in the long run. And I think another important factor to keep in mind is a lot of these differences in upward mobility that we're seeing across areas emerge at relatively early ages.

　　By the time kids are 18, you're seeing a lot of these differences in teenage pregnancy¹⁷ rates and college attendance rates. And so that suggests to me that we need to be intervening relatively early on, consistent actually with the earlier segment, on food insecurity, where researchers have found in a variety of contexts that it's those early formative years, as well as around age 10, age 15, that is the point at which differences really can emerge and where intervention¹⁸, I think, is important.

　　JEFFREY BROWN: All right, Raj Chetty -- Raj, OK, let me ask you one more question.

　　You mentioned that, you know, upward mobility is cited regularly by politicians nowadays. Are they -- have they just missed something?

　　RAJ CHETTY: Well, I think people's perceptions about trends in mobility may not quite have been accurate, but I think the increased focus on income mobility as a key policy priority is absolutely right on.

　　And I think our study reinforces that message that there are significantly lower levels of upward mobility than you might like in many parts of the U.S. Even though that hasn't changed significantly over time, we should be concerned that there is a persistent⁵ problem in many parts of America, like Atlanta, like Charlotte, like Indianapolis, and many other cities, where kids from disadvantaged backgrounds really don't have great odds of succeeding.

　　And I think it's critical to identify policies that can change that situation.

　　JEFFREY BROWN: And where is your study going from here? Because we did have that conversation last year, when you were looking at geography. And now you come up looking at upward mobility. Where do you go from here?

　　RAJ CHETTY: Yes, that's right.

　　So all this work is part of what we're calling the Equality of Opportunity Project. And the goal of this project is to use scientific methods and big data to try to identify what the determinants of upward mobility are and how we can improve kids' outcomes from disadvantaged backgrounds.

　　One of the things we are going to study next is look at people who move across areas. Take a person who moves from Atlanta to San Jose or Atlanta to Salt Lake City. How do their kids' outcomes change, and what can we learn about what the exact causal factors are by looking at people who move across different areas?

　　JEFFREY BROWN: All right, Raj Chetty, thanks so much.

　　RAJ CHETTY: Thank you. My pleasure.

1 economists   

n.经济学家，经济专家( economist的名词复数 )

参考例句：

• The sudden rise in share prices has confounded economists. 股价的突然上涨使经济学家大惑不解。
• Foreign bankers and economists cautiously welcomed the minister's initiative. 外国银行家和经济学家对部长的倡议反应谨慎。 来自《简明英汉词典》

2 prospects   

n.希望，前途(恒为复数)

参考例句：

• There is a mood of pessimism in the company about future job prospects. 公司中有一种对工作前景悲观的情绪。
• They are less sanguine about the company's long-term prospects. 他们对公司的远景不那么乐观。

3 mobility   

n.可动性，变动性，情感不定

参考例句：

• The difference in regional house prices acts as an obstacle to mobility of labour.不同地区房价的差异阻碍了劳动力的流动。
• Mobility is very important in guerrilla warfare.机动性在游击战中至关重要。

4 odds   

n.让步，机率，可能性，比率；胜败优劣之别

参考例句：

• The odds are 5 to 1 that she will win.她获胜的机会是五比一。
• Do you know the odds of winning the lottery once?你知道赢得一次彩票的几率多大吗？

5 persistent   

adj.坚持不懈的，执意的；持续的

参考例句：

• Albert had a persistent headache that lasted for three days.艾伯特连续头痛了三天。
• She felt embarrassed by his persistent attentions.他不时地向她大献殷勤，使她很难为情。

6 persistently   

ad.坚持地；固执地

参考例句：

• He persistently asserted his right to a share in the heritage. 他始终声称他有分享那笔遗产的权利。
• She persistently asserted her opinions. 她果断地说出了自己的意见。

7 prescriptions   

药( prescription的名词复数 )； 处方； 开处方； 计划

参考例句：

• The hospital of traditional Chinese medicine installed a computer to fill prescriptions. 中医医院装上了电子计算机来抓药。
• Her main job was filling the doctor's prescriptions. 她的主要工作就是给大夫开的药方配药。

8 stagnated   

v.停滞，不流动，不发展( stagnate的过去式和过去分词 )

参考例句：

• The balloting had stagnated, he couldn't win. 投票工作陷于停顿，他不能得胜。 来自辞典例句
• His mind has stagnated since his retirement. 他退休后头脑迟钝了。 来自辞典例句

9 offset   

n.分支，补偿；v.抵消，补偿

参考例句：

• Their wage increases would be offset by higher prices.他们增加的工资会被物价上涨所抵消。
• He put up his prices to offset the increased cost of materials.他提高了售价以补偿材料成本的增加。

10 detrimental   

adj.损害的，造成伤害的

参考例句：

• We know that heat treatment is detrimental to milk.我们知道加热对牛奶是不利的。
• He wouldn't accept that smoking was detrimental to health.他不相信吸烟有害健康。

11 consequential   

adj.作为结果的，间接的；重要的

参考例句：

• She was injured and suffered a consequential loss of earnings.她受了伤因而收入受损。
• This new transformation is at least as consequential as that one was.这一新的转变至少和那次一样重要。

12 precisely   

adv.恰好，正好，精确地，细致地

参考例句：

• It's precisely that sort of slick sales-talk that I mistrust.我不相信的正是那种油腔滑调的推销宣传。
• The man adjusted very precisely.那个人调得很准。

13 relatively   

adv.比较...地，相对地

参考例句：

• The rabbit is a relatively recent introduction in Australia.兔子是相对较新引入澳大利亚的物种。
• The operation was relatively painless.手术相对来说不痛。

14 remains   

n.剩余物，残留物；遗体，遗迹

参考例句：

• He ate the remains of food hungrily.他狼吞虎咽地吃剩余的食物。
• The remains of the meal were fed to the dog.残羹剩饭喂狗了。

15 segregation   

n.隔离，种族隔离

参考例句：

• Many school boards found segregation a hot potato in the early 1960s.在60年代初，许多学校部门都觉得按水平分班是一个棘手的问题。
• They were tired to death of segregation and of being kicked around.他们十分厌恶种族隔离和总是被人踢来踢去。

16 cohesiveness   

n. 粘合，凝聚性

参考例句：

• The Bogor Goals concern APEC's credibility, cohesiveness and future development. 茂物目标事关亚太经合组织的信誉、凝聚力和未来发展。
• One of the most important properties of a work team is cohesiveness. 工作小组的最重要特征之一是凝聚力。

17 pregnancy   

n.怀孕，怀孕期

参考例句：

• Early pregnancy is often accompanied by nausea.怀孕早期常有恶心的现象。
• Smoking during pregnancy increases the risk of miscarriage.怀孕期吸烟会增加流产的危险。

18 intervention   

n.介入，干涉，干预

参考例句：

• The government's intervention in this dispute will not help.政府对这场争论的干预不会起作用。
• Many people felt he would be hostile to the idea of foreign intervention.许多人觉得他会反对外来干预。