Birth Rates are the number of live births per 1,000 persons in a specified group. Birth rates on PeriStats are calculated as the number of live births per 1,000 women 15-44 years of age, often referred to as a fertility rate. The denominator for this calculation is based on population data from the U.S. Census Bureau, available through the National Center for Health Statistics Web site. For more information, see calculation notes on Population.
Percentage of births calculations show the distribution of live births by race, race/ethnicity, and maternal age. Calculations are based on the number of live births in a specified group divided by all live births, multiplied by 100. Data for distributions by race and maternal age sum to 100 percent. Distributions by race/ethnicity do not sum to 100% due to live births missing data on ethnicity.