Immigration and Fertility in the U.S.

描述(申请人提供)：鉴于美国的生育率和死亡率相对较低，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。尽管人们对前者给予了相当大的关注，但移民对生育率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，从定义上讲，国家生育模式将越来越多地由他们的行为决定。1990至2010年间，美国移民妇女所生子女的比例从16%上升到23%。今天，如果没有移民的生育率，美国每年的出生率将减少近100万。这一影响突出表明，需要对移民生育率进行系统分析，包括开发人口统计技术，明确区分移民对人口增长的贡献及其对生育率的影响。特别有问题的是，对移民和生育时机之间的相互作用缺乏了解。标准的人口统计学方法通常假设这两个组成部分是不相关的。然而，研究强调，移民会严重扭曲生育年龄模式。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高估。由于特定于年龄 生育率是人口预测的一个关键组成部分，这种高估扭曲了对国家人口规模、年龄和种族结构的预测。因此，我们的具体目标是：1)衡量2000-2010年期间移民对美国生育率的贡献及其随时间和种族群体的变化，区分拉美裔、亚裔和非拉美裔黑人和白人；2)在种族/民族类别内，分开国家原籍群体，并衡量他们的生育率贡献，详细阐述移民国籍的变化对美国生育率的影响；3)评估标准生育率衡量方法的适用性，以及移民经历在这一时期和不同种族群体之间的变化。具体来说，我们将评估移民造成的节奏扭曲在影响标准时期生育率指标方面的作用；4)制定和测试明确考虑移民动态的生育率指标，以衡量移民在一段时间内和跨族裔群体的生育率。具体而言，这意味着承认移民妇女的生育是在移徙之前和之后发生的；必须将这两个组成部分分开，以衡量移徙对生育率的具体贡献；以及5)将这些措施纳入人口预测方法，并评估其对2000-2010年预测的人口变化的影响。我们还将生成一套到2050年的新的人口预测，并将它们与人口普查估计进行比较。

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.