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。

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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。

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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。

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The state-by-state information is not yet complete, but Marc Perry says demographers found a clear trend in population growth.

VOA: special.2011.03.14

"The government's own figures, according to demographers at Oxford University,show that the indigenous British the people who've been here."

VOA: standard.2009.10.23

Don't ask the sociologists, the demographers, the advertising agencies, and certainly not the tobacco companies.

CNN: No Easy Answer To Teen Smoking

Still, many Chinese and Western economists and demographers say that urbanization can be a double-edged sword.

WSJ: China's Population Shifts to Cities

Around 1970, many African-Americans began moving back to the South, historians and demographers say.

CNN: Family roots lure many African-Americans back to South