Immigration and Fertility in the U.S.

描述（由申请人提供）：鉴于美国目前相对较低的生育率和死亡率水平，未来的人口增长和结构将越来越多地受到移民的影响。这种移民效应源于两种机制：净移民和外国出生人口的生育率。虽然对前者给予了相当大的关注，但移民对生育的贡献仍然知之甚少。这是有问题的，因为随着移民人口的增长，国家的生育模式将越来越多地由他们的行为决定。从1990年到2010年，移民妇女所生美国孩子的比例从16%上升到23%。今天，如果没有移民的生育能力，美国每年的新生儿数量将减少近100万。这种影响突出表明有必要系统地分析移民生育率，包括发展能够明确区分移民对人口增长的贡献及其对生育率的影响的人口统计技术。尤其有问题的是缺乏对移民和生育时间之间相互作用的理解。标准的人口统计技术通常假设这两个组成部分是分离的。然而，研究强调，移民会严重扭曲生育的年龄模式。由于没有考虑到移民对生育时间的影响，导致对移民生育率时期水平的严重高估。因为不同年龄组

DESCRIPTION (provided by applicant): Given the relatively low fertility and mortality levels prevailing in the United States, the future growth and structure of the population will be increasingly affected by immigration. This immigration effect stems from two mechanisms: net migration and the fertility of the foreign-born. While considerable attention has been devoted to the former, immigrants' fertility contribution remains poorly understood. This is problematic because as the immigrant population grows, national fertility patterns will by definition be increasingly determined by their behavior. Between 1990 and 2010 the share of U.S. children born to immigrant women increased from 16 to 23%. Today, without the fertility of immigrants there would be nearly one million fewer U.S. births annually. This impact highlights the need for systematic analyses of immigrant fertility, including the development of demographic techniques that can clearly separate the population growth contribution of immigration from its fertility effet. Particularly problematic is the lack of understanding of the interaction between immigration and fertility timing. Standard demographic techniques generally assume the two components are disconnected. However, studies have highlighted that migration can significantly distort the age-pattern of childbearing. Failure to account for the impact of immigration on the timing of births results in a substantial overestimation of period levels of immigrant fertility. Since age-specific fertility rates are a key component of population projections, this overestimation distorts projections of the size, age, and ethno-racial structure of national populations. Thus, our specifi objectives are to 1) Measure the contribution of immigrants to U.S. fertility for the period 2000-2010 and its variation over time and by ethnic group, distinguishing between Hispanics, Asians, and non-Hispanic blacks and whites; 2) Separate, within racial/ethnic categories, national origin groups and measure their fertility contribution elaborating on the role that changing immigrant national origin has on U.S. fertility; 3) Assess the applicability of standard fertility measures t the immigrant experience and its variation over the period and across ethno-racial groups. Specifically, we will assess the role of tempo distortions resulting from immigration in affecting standard period fertility measures; 4) Develop and test fertility measures that explicitly take int account the dynamics of migration to measure the fertility of immigrants over time and across ethno-racial groups. Specifically, this implies recognizing that births to immigrant women occur before and after migration; separating the two components is necessary to measure the fertility- specific contribution of immigration; and 5) Incorporate these measures into population projection methods and assess their impact on predicted population change for 2000-2010. We will also generate a new set of population projections through 2050 and compare them to Census estimates.