R Plomin and I J Deary have this to say:
" ... Assortative mating is greater for intelligence (spouse correlations ~0.40) than for other behavioural traits such as personality and psychopathology (~0.10) or physical traits such as height and weight (~0.20)."
Here's what a correlation of 0.4 looks like (top right).
Marginal Revolution gets excited about this result though:
"Nordsletten and colleagues find an amazing amount of assortative mating within psychiatric disorders.They conclude:
"Spouse tetrachoric correlations are greater than 0.40 for attention-deficit/hyperactivity disorder (ADHD), autism spectrum disorder (ASD), and schizophrenia.
"The next highest spouse correlation emerged for substance abuse (range, 0.36-0.39).
"Assortative mating was significant but far less substantial for other disorders, such as affective disorders (range, 0.14-0.19)."
"Beyond genetics and genomics, assortative mating matters because it means that the person closest to an individual with a psychiatric disorder is also likely to have psychiatric problems, which could exacerbate problems for both spouses and their offspring."The ubiquity of assortative mating - who knew?