To develop more accurate population forecasts, demographers have to know a great deal more than now about the social and economic determinants of fertility.

为了做出更准确的人口预测，人口统计学家必须比现在更多地了解生育率的社会和经济决定因素。

Demographers reckon that three quarters of humanity could be city dwelling by 2050, with most of the increase coming in the fast growing towns of Asia and Africa.

人口学家估计，到2050年，将有四分之三的人类居住在城市，其中大部分将来自亚洲和非洲快速发展的城镇。

Working from what America already knows about itself, the bureau's experts and other demographers offer an irresistible, if clouded, crystal ball among their visions.

根据美国已经了解的情况，统计局的专家和其他人口统计学家在他们的视野中提供了一个不可抗拒的水晶球。

Demographers try to predict social fluidity.

人口统计学家试图预测社会流动性。

Demographers call this evolution the demographictransition.

人口统计学家称这种演化为人口过渡。

Some Chinese demographers worry that the country will get old before getting rich.

一些中国人口专家担忧届时可能面临未富先老的问题。

Selectivity of human migration long been the focus of demographers and economists.

人口迁移的选择性一直以来都是人口学家和经济学家关注的焦点。

But Mr. Cai and other demographers estimate the real rate is closer to 1.5 children.

但是蔡先生和其他人口统计学家估计，真实的比率是接近1.5。

Until recently most discussion in China has been confined to academic demographers.

直到最近，在中国大多数的讨论一直局限于人口统计学家的学术性研讨上面。

Because this is a demographic that has traditionally been overlooked by demographers.

因为这一部分人口一直以来都被人口学家忽略。

Selectivity of human migration has long been the focus of demographers and economists.

人口迁移的选择性一直以来都是人口学家和经济学家关注的焦点。

Of greater concern to Chinese demographers are the social and economic effects of these trends.

对中国人口学家们来说，最大的担心是这个人口发展趋势对社会、经济的影响。

Having too many people onthe planet is no longer demographers' chief worry; now, having too few is.

地球人人口太多不再是人口学家最大的担心；他们现在反过来担心人口太少。

Demographers have often noted that most of the emerging world will stay young while the rich world ages.

人口学家已经注意到：当富裕国家的人口变老时，大多数新兴国家的人口仍然非常年轻。

Demographers forecast that Memphis will soon become the nation's first majority black metropolitan region.

人口学家曾预言，孟菲斯将成为全国第一个以黑人为主的都市地区。

Demographers have calculated that the world's population will double by the end of the twentieth century.

人口统计学家推算到了二十世纪末世界人口会加倍。

In other countries, demographers have also grappled with theories of baby booms linked to specific events.

在其他国家，人口统计学家还坚持着婴儿潮与特定事件有关联的理论。

Many demographers reckon it is already too late to lift Japan's birth rate, now at 1.43 children per woman.

许多人口学者估计现在已经太迟而提高不了日本的出生率了，现在的比率是平均一个妇女有1.43个孩子。

Some of the sociologists, psychologists and demographers who study this new life stage see it as a good thing.

一些研究这一新的生活阶段的社会学家、心理学家和人口统计学家把这样现象看成是一件好事。

Many demographers believe that around the end of the century, the global population will gradually level off.

许多人口统计学家认为在本世纪末期的某个阶段，世界人口将趋于平稳。

Census demographers noted that the percentage of never-married black women 55 and older rose to 13 percent in 2009.

人口普查统计发现，未婚的超过55岁的黑人女性的比例在2009年上升至13%。

By 2050, most demographers agree that non-Hispanic white people will be a minority in the overall national population.

大多数人口统计学家一致认为，到2050年，拉美裔以外的白种人将成为美国全国总人口中的少数。

This year, World Habitat Day falls during the month when demographers predict our planet's seven billionth inhabitant will be born.

今年，在世界人居日所在的这个月，据人口学家预言，将诞生我们星球上第70亿个居民。