Monday, August 28, 2006

Cognitive decline in modern america


This table give various values of WORDSUM (a test of verbal ability)

and their relation to:

The number of children per adult (over 35 years old). (Trend line)
The age at the birth of the first child. (Trend line)
Current and future % of population (See important note on heritability)

Also, the current mean wordsum is 5.99 but will decline by 0.22 Wordsum* Heritability(Wordsum) in 25 years and by 0.44 Wordsum*Heritability (Wordsum) in 50 years.

I use this age as a generation length (incorrectly, but it should be only a marginal error that doesn't change the main point)
I can compute by how much each given group will increase, and the likely population over numerous years.

Note:

The raw difference in cognitive decline need to be multiplied by the heritability of WORDSUM, which is not known. (A fair guess might be 0.6 to 0.8)

(Do not consider the future group with a wordsum value of 4 to actually obtain a value of 4, I only use the data this way because it is more easy) Don't forget that little regression to the mean concept.

Source GSS data

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