In a Down Economy, Fewer Births
Appendix 2: Methodology
Birth data were obtained from the National Center for Health Statistics (NCHS). NCHS birth statistics for 2009 are preliminary and include 99.95% of all births in that year. Birth statistics for 2010 are provisional.
Vintage 2009 population estimates provided by the U.S. Census Bureau were used in calculating birth rates.
Birth rates are measured using the general fertility rate (GFR), which is the number of births divided by the number of women of childbearing age (15-44).6
When the annual change in number of births is within the range of plus or minus 0.5%, this change is considered “leveling off.” Similarly, a fertility rate is defined as “leveling off” if its annual change is within the range of plus or minus 0.5%.
In choosing economic indicators to use in this report, we were most interested in finding those variables that are good indicators of an individual’s experiences with the economic downturn; that are available at the state level; and that use standardized metrics, which allow for cross-state comparisons. Ultimately, seven indicators relating to income, employment and the housing market were tested to see whether their variations were associated with variations in fertility at the state level:
- Annual Per Capita Income, calculated using data from the Bureau of Economic Analysis, and the U.S. Census Bureau, and adjusted to year 2009 dollars using the National Consumer Price Index-U. The other major estimate of income is household income as estimated by the U.S. Census Bureau from its Annual Social and Economic Supplement to the Current Population Survey. Both measures of income are comprehensive, including wages and salaries, and also interest, rental and other sources of income. They also trend similarly across the business cycle. We chose to use the per capita income measure because it is readily available at the state level. Per capita income is also a more comprehensive measure because it includes employer contributions to pension funds and health and other insurance plans.
- Real Per Capita Gross Domestic Product, by state, using 2005 dollars, available from the Bureau of Economic Analysis
- Annual Employment Rate for the civilian noninstitutionalized workforce (persons ages 16 and older), calculated using data available from the Bureau of Labor Statistics
- Annual Unemployment Rate, available from the Bureau of Labor Statistics
- Initial Unemployment Claims for the second quarter, available from the Department of Labor
- Foreclosure Rate, the percent of all housing stock in foreclosure, as determined by RealtyTrac
- House Price Index (HPI) for the second quarter, which measures single-family house prices, available through the Federal Housing Finance Agency
- In 2008, women ages 15-44 accounted for 99.7% of all births in the U.S. ↩