How did you come to that conclusion? I looked for that in the figures, but I couldn’t find what percentage came into money from an inheritance. Perhaps it’s placed in the 12% ‘Diversified/Other’ category, but the impression I got from the article was that they tallied how the money was earned in the first place, not where the ones holding the purse got it from.
I believe your interpretation of the article in this aspect is incorrect. For instance, 4 of the top 10 spots are taken up by members of the Walton family. Those people inherited their wealth from Bud and Sam Walton, the founders of Wal*Mart.