title: Interpreting the components of time trends.
abstract: "Procedures for decomposing differences between two populations--for example, into the part that is due to differences in age-specific rates and the part that is due to differences in age distributions--have been used to decompose time trends into the part that is due to changes occurring within cohorts and the part that is due to the gradual replacement of older by younger cohorts.  It is not clear what is accomplished by such a decomposition of a trend, however.  Decomposition does not tell us what types of variables may be the root causes of a trend, and there is a real danger that such a decomposition will confuse rather than clarify."  The concepts are illustrated using U.S. data on racial prejudice and marijuana use.  A response by Glenn Firebaugh defending decomposition methods is included (pp. 439-46).
authors.forename: W L
authors.initials: WL
authors.lastname: Rodgers
mesh_terms: D000367:Age Factors; D000569:Americas; D015331:Cohort Studies; D003710:Demography; D019049:Developed Countries; D008722:Methods; D009656:North America; D011153:Population; D011154:Population Characteristics; D011157:Population Dynamics; D012106:Research; D013997:Time Factors; D014481:United States
keywords: Age Factors; Americas; Cohort Analysis; Demographic Factors; Developed Countries; Methodological Studies; North America; Northern America; Population; Population Characteristics; Population Dynamics; Research Methodology; Time Factors; United States