In the Wikipedia page of Johnson O' Connor, there is a sentence says (I add the boldness):
A person’s vocabulary level was the best single measure for predicting occupational success in every area.
Wow, so does this mean that everyone in this forum will be successful in every area? :)
However, all four reference links in that paragraph in Wikipedia aren't helpful. Either they are inaccessible online, or 50 year-old or more. I even have visited the site of Johnson O' Connor Research Foundation, but once again I can't find any useful information. The best one I could found is very generic.
Since "occupational success in every area" is too broad or vague the following: are there any studies besides these generic references that vocabulary level is a good measure for high income (as a measure of "success") later?