Data from the General Social Survey (GSS) collected in the years 1990-1996 are examined for the relationship between fertility and intelligence as measured by vocabulary. The results show that the relation between fertility and intelligence has been consistently negative for successive birth cohorts from to 1900 to 1979, indicating the presence of dysgenic fertility for all of the 20th century studied thus far. The most recent cohort for which fertility can be regarded as complete is that born in the years 1940-1949. In this cohort, the decline of genotypic intelligence arising from the negative association between intelligence and fertility is estimated at 0.90 IQ points per generation. The decline of genotypic intelligence of Whites is estimated at 0.75 IQ points a generation.