This entry provides a brief overview of the field of social demography, the components of population change, projections for future population growth, and recent transformations in population composition pertaining to age, race, and ethnicity. Trends that shape family household structure (for example, marriage, divorce, cohabitation, and nonmarital child bearing) are also considered, as are trends pertaining to the distribution of income, wealth, and poverty. Population trends given particular attention include the growth of class-based disparities in marriage and nonmarital child bearing, the contributions of immigration to population growth and diversity, and a disturbing increase over recent decades in the prevalence of poverty among children of immigrants.