摘要：当全美生育率持续下滑，为何犹他州一个小镇却婴儿潮涌动？这里的孩子比大人多，出生率高达全国平均水平两倍。背后不是宗教传统那么简单，而是年轻父母用脚——他们迁徙至此，只为在“儿童友好型社区”生儿育女。《经济学人》最新调研揭示：高收入高学历群体正在成为生育新主力，而

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The Economist ｜Free exchange

经济学人 ｜ 自由交换

The new economics of babymaking

生育的新经济学

A postcard from one of America’s youngest towns

来自美国最年轻城镇的一则报道

在盐湖城南几英里处，犹他县深处的佩森镇正在举行游行。蹒跚学步的孩子们在卡车之间奔跑，卡车上牵引着载有啦啦队员和橄榄球运动员的花车。七位选美皇后从一个巨大的西瓜模型上挥手致意；下一辆花车上载着36名风笛手。在这个年度庆典中，每一位表演者都是儿童。总共需要两个小时，他们才能全部涌上街头。

在2008年至2024年间，美国普通女性的生育率下降了四分之一。该国人口正在老龄化，并且如果出生率保持低位，人口最终将会减少。但在佩森镇，与大多数城镇不同，儿童的数量仍然超过成人。2024年，犹他县出生的婴儿数量比十年前还要多。尽管在整个犹他州范围内，生育率的下降速度超过了美国平均水平，但该县的新生儿数量几乎比美国任何其他地方都多。据市长办公室称，在南部地区，出生率是全国平均水平的两倍——而且还在上升。

长期以来，研究女性选择的经济学家模型都假设，出生率下降是收入增加所致。在一个富裕的、精英治理的国家，夫妻有理由在教育和其他提升子女生活机会的方面投入更多，从而减少了用于生育更多孩子的资源。随着更多女性加入劳动大军，生养孩子的机会成本也在上升，因为原本用于抚育孩子的时间可以用于发展事业。经济学家们倾向于认为，正是由于这些原因，美国富裕女性生育的孩子比贫困女性要少。

但最近的研究和生育趋势挑战了这一共识。 在高收入国家内部，最富裕地区的女性现在生育的孩子最多，而非最少 。最贫困女性的出生率下降得最快。并且自2010年以来，受过高等教育的女性生育了更多的孩子。

换句话说，拥有富裕且不断扩大家庭的犹他县，概括了经济学家们难以理解的关于美国生育率的状况。在这里，并非当地人口抵抗了其他地区导致生育率下降的社会力量。相反，许多最新的父母本身就是新来者，他们搬到该县就是为了生孩子。 这里对儿童友好的基础设施和年轻家庭的高密度具有强大的吸引力 。这些新来者说明了美国人口结构变化中一个未被充分认识到的后果。随着全美各地的城市逐渐"变灰"（老龄化），想要成为父母的人将会涌向那些仍然优先考虑儿童的社区。

摩门教徒有助于解释犹他县不寻常的人口结构——但并非你想象的那种方式。他们长期以来一直占该县人口的大多数。典型的去教堂做礼拜的成年人成长在有四个孩子的家庭中，比美国平均水平多两个。当其他地区出生率下降时，佩森镇建造了更多学校，改造了公共空间，并提供了儿童保育服务。邻近的普罗沃镇（杨百翰大学所在地）的大部分学生宿舍在建造时都包含了供儿童使用的空间。在其他地方，女性似乎为了腾出时间给事业而减少生育。但在犹他州，工作的女性较少，而且当地的想法是，她们最终会拥有与母亲辈规模相当的家庭。

在其后的35年里，事情并未如此发展。摩门教女性的生育率下降幅度超过了其他人群。到2019年，超过一半的摩门教女性生育的孩子少于三个。犹他州的出生率下降速度比任何其他州都要快。然而，住房、交通和教育子女仍然是这些宗教郊区社区的组织原则。这吸引了大量的移民潮，主要是来自美国其他地方的新婚夫妇和年轻家庭。例如，目前在犹他县生活的70万人中，约有10万人是2014年以后到来的。在该县东部边界群山环抱的富裕小镇阿尔派恩，一位摩门教退休老人指向他所在的死胡同。在12栋宽敞的房屋中，除他家之外，其余均由2010年后迁入犹他州的家庭购得。如今，形形色色的父母们挤满了当地的博物馆、公园和游行队伍。

很少有人口学家思考过，在一个老龄化的世界里，新父母们会如何行事。大多数人仍然关注出生率下降带来的连锁反应。随着老年人口队伍的膨胀，他们将吸引政策制定者的注意力。 一个令人担忧的后果可能是，由于缺乏国家支持和同伴父母，夫妻可能生育更少的孩子 。但许多人决心已定，并且似乎很可能会相互寻找。

难道就没人想想孩子们吗？

因此，犹他县或许可以为美国其他渴望提高生育率的地区提供一个范例。在2023年发表的一项研究中，西北大学的马蒂亚斯·德普克及其同事评估了生育热点地区的共同点。他们发现， 在政策制定者建立了儿童保育计划并引入弹性工作时间的地区，出生率保持得最好 。社会规范也很重要。生活在成年人社交生活围绕孩子展开的地方的人们，往往生育更多孩子。

许多政治家担心依赖移民来弥补生育不足。佩森镇表明，这未必全是坏事。新来者很富有：他们必须如此才能负担得起该地区的房屋，过去十年当地房价已翻了一番。这为州财政带来了提振。而且，那些搬到该地区组建家庭的人拥有大学学位的可能性似乎也越来越大，这反映了一种全国趋势。根据德普克先生的说法，受教育程度最高的女性的生育率正在上升。

大多数大城市和人口众多的州尚未完全变得老迈和"灰暗"。尽管如此，当本专栏作者看着另一辆花车（这次载满了小提琴手）驶过佩森镇时，所展现出的巨量青春活力让人感到既陌生又惊讶。这也是令人愉快的。一个城镇将儿童置于其公共生活的核心，这已经多么罕见。■

Afew milessouth of Salt Lake City, deep in Utah County, the town of Payson is on parade. Toddlers run between trucks that tug floats carrying cheerleaders and footballers. Seven beauty queens wave from a giant watermelon; the next float bears 36 bagpipers. Every performer in this annual celebration is a child. All told, it takes them two hours to pour onto the streets.

Between 2008 and 2024, the fertility of America’s average woman fell by a quarter. The country’s population is ageing and, should birth rates stay low, will eventually shrink. But in Payson, unlike most towns, children still outnumber adults. More babies were born in Utah County in 2024 than a decade earlier. Although fertility has fallen faster than the American average in the wider state, the county makes more babies than almost anywhere else in America. In southern districts, according to the mayor’s office, the birth rate is twice the national average—and rising.

Economists modelling women’s choices have long assumed that falling birth rates are down to rising incomes. In a rich, meritocratic country, couples have reason to spend more on education and other ways to boost their offspring’s life-chances, leaving less to spend on additional babies. As more women join the labour force, the opportunity cost of having a child rises, since child-rearing time could instead be spent advancing a career. It is for these reasons, economists have tended to think, that rich women in America have fewer children than their poorer peers.

But recent research and birth trends have challenged this consensus. Withinhigh-income countries, women in the richest places now have the most children, rather than the fewest. Birth rates among the poorest women are falling fastest. And since 2010, highly educated women have been having more children

In other words Utah County, with its rich, expanding families, encapsulates what economists struggle to understand about American fertility. Here, it is not that the population has resisted the social forces reducing fertility elsewhere. Rather, many of the newest parents are newcomers themselves, who moved to the county to have babies. Its child-friendly infrastructure and density of young families are a potent draw. These new arrivals illustrate an underappreciated consequence of America’s changing demography. As cities across the country get greyer, would-be parents will flock to those communities that still prioritise children.

Mormons help explain Utah County’s unusual demography—but not in the way you might expect. They have long made up the majority of the county’s population. The typical temple-going adult grew up in a family with four children, two more than the average American. As birth rates fell elsewhere, Payson built more schools, adapted public spaces and provided child care. Most student housing in the neighbouring town of Provo, home to Brigham Young University, was built to include space for children. Elsewhere, women seemed to be having fewer babies in order to make time for their careers. But fewer women worked in Utah, and locally the thinking was that they would end up having similar size families to those of their mothers.

In the intervening 35 years, that is not how things have turned out. The fertility of Mormon women has dropped by more than that of the rest of the population. By 2019 more than half had fewer than three children. Birth rates are falling faster in Utah than in any other state. Yet housing, transporting and educating children is still the organising principle of these religious suburbs. That has attracted a flood of migration, mostly newlywed couples and young families from elsewhere in America. Of the 700,000 people now living in Utah County, for instance, some 100,000 have arrived since 2014. In Alpine, an affluent town nestled in the mountains on the county’s eastern border, one Mormon retiree points down his cul-de-sac. Out of 12 sprawling houses, all but his have been bought by families that arrived in Utah since 2010. A diverse set of parents now packs local museums, parks and parades.

Few demographers contemplate how new parents will behave in an ageing world. Most are still caught on the knock-on effects of fewer births. As the ranks of the elderly swell, they will soak up policymakers’ attention. A worrying consequence might be that, with little state support and few other parents, couples might have even fewer children. But many will remain determined, and seem likely to seek one another out.

Won’t somebody please think of the children?

Thus Utah County might provide an example for other parts of America keen to have more babies. In a study published in 2023, Matthias Doepke of Northwestern University and colleagues assessed what fertility hotspots had in common. They found that birth rates held up best in places where policymakers set up child-care schemes and introduced flexible working hours. Social norms also mattered. People living in places where adults’ social lives revolved around children tended to have more of them.

Many politicians worry about relying on migration to make up for birth shortages. Payson shows that it need not be all bad. New arrivals are rich: they have to be to afford houses in the area, the prices of which have doubled over the past decade. That provides a boost to the state’s coffers. And those moving to the area to start families also seem increasingly likely to have university degrees, which reflects a national trend. According to Mr Doepke, birth rates among the most educated women are rising.

Most big cities and populous states are not yet entirely old and grey. Still, as your columnist watches another float roll through Payson (packed with fiddlers, this time) the sheer quantity of youthful exuberance on display feels startingly unfamiliar. It is pleasant, too. How rare it is already for a town to put children at the heart of its public life. ■

来源：左右图史