Numerator
Number of deaths of infants aged 27 days and under
Methodology
To create linked data files, death certificates are linked with corresponding birth certificates for infants who die in the U.S. before their first birthday. The linked file is used for calculating infant mortality rates by race and ethnicity because these variables are more accurately collected on the birth certificate than the death certificate.
Depending upon county population size, the period county percent for the most recent 3, 5, or 10 years is reported.