October 12, 2011

In a Down Economy, Fewer Births

Appendix 2: Methodology

Fertility Data

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%.

Economic Data

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:

  1. In 2008, women ages 15-44 accounted for 99.7% of all births in the U.S.