The vocabulary of U.S. college graduates was lower in the 2010s vs. the late 1970s.

From Declines in vocabulary among American adults within levels of educational attainment, 1974–2016 by Jean M. Twenge, W. Keith Campbell, Ryne A.Sherman. From the Abstract.

Highlights

• When controlled for educational attainment, adults' vocabulary skills have declined.

• The vocabulary of U.S. college graduates was lower in the 2010s vs. the late 1970s.

• Vocabulary declined across all levels of educational attainment.

• The decline in vocabulary is primarily a time period effect.

Abstract

We examined trends over time in vocabulary, a key component of verbal intelligence, in the nationally representative General Social Survey of U.S. adults (n = 29,912). Participants answered multiple-choice questions about the definitions of 10 specific words. When controlled for educational attainment, the vocabulary of the average U.S. adult declined between the mid-1970s and the 2010s. Vocabulary declined across all levels of educational attainment (less than high school, high school or 2-year college graduate, bachelor's or graduate degree), with the largest declines among those with a bachelor's or graduate degree. Hierarchical linear modeling analyses separating the effects of age, time period, and cohort suggest that the decline is primarily a time period effect. Increasing educational attainment has apparently not improved verbal ability among Americans. Instead, as educational attainment has increased, those at each educational level are less verbally skilled even though the vocabulary skills of the whole population are unchanged.

We are paying more and more for education. People are spending more and more time being educated. And we are getting more stupid? At least in vocabulary?

Perhaps. Wish I could see the detail and whether the effect size is material.

Perhaps it reflects the increase of foreign born population (and non-English speakers) which was something like 4.7% in 1975 and is approaching 15% today.