ON THE APPLICATION OF DECOMPOSITION METHODS/YANG ET AL. RESPOND

The first component answers the query of what change we would have seen if the age-parity distribution had been at its average value throughout but the specific rates had changed as observed, whereas the second answers the query of what change we would have seen if the age-parity distribution had changed as observed after 1980 but the specific rates had been at their average values throughout At best, these queries each use standards achieved at some unknown interim time, when the standardizing quantities were all at their average values. Request for reprints should be sent to Quanhe Yang, PhD, Division of Birth Defects and Developmental Disabilities, National Center on Birth Defects and Developmental Disabilities, Centers for Disease Control and Prevention, 1600 Clifton Rd, Mail Stop £-86, Atlanta, GA 30333 (e-mail: qayO@cdc.gov).