Age, Period, and Cohort Trends in Americans’ Vocabulary Knowledge

Liying Luo, University of Minnesota

For more than two decades researchers have been debating the extent to which Americans’ vocabulary knowledge varies as a function of age, period, and cohort. This debate has important implications for educational policy and practice, and speaks to America’s competitiveness in the global economy. Unfortunately, prior assessments of age, period, and cohort trends in vocabulary knowledge have either assumed a priori that one of the three does not matter or else have relied on problematic statistical assumptions. We revisit this debate using a new method. We find that vocabulary knowledge increases through about age 70; it declined in the 1980s but increased later; and, on average, vocabularies rose across the 1890 through early baby boom cohorts and then lowered across most more recent cohorts. We explore explanations for these trends, and draw preliminary conclusions about the roles of the quality of school and word obsolescence.