Linked Birth/Infant Death Data Series

These data are provided by the United States Department of Health and Human Services, National Center for Health Statistics to be used in determining infant mortality rates. Each data collection consists of two types of files. The first file type provides linked records of live births and deaths of children born in the United States (to residents and nonresidents). This file is called the Numerator File. The second file type consists of live births in the United States and is referred to as the Denominator File. Beginning in 1989, a number of items were added to the U.S. Standard Certificate of Birth. These changes and/or additions led to the redesign of the linked file record layout for this series and to other changes in the linked file. In addition, variables from the Numerator File were added to the Denominator File to facilitate processing, and from 1989 on this file is called the Denominator-Plus File. A third file type was added in 1989 called the Unlinked File, which consists of infant death records that could not be linked to their corresponding birth records. In 1995, data for Puerto Rico, the Virgin Islands, and Guam were included, and there was a change in format of the linked files, which were released in two different formats, period data and birth cohort data.