I spent the last 25 minutes trying to find out exactly that, and have so far come up nearly blank, but I agree that dollars inherited is a way more useful quest

I spent the last 25 minutes trying to find out exactly that, and have so far come up nearly blank, but I agree that dollars inherited is a way more useful question. The meme of "a high percent of people who are millionaires are first-generation millionaires" is pervasive. Googling this returns mostly investment scheme websites and CNBC/USA Today/etc clickbait quoting "The Millionaire Next Door", and talking about how "If They Did It, You Can Do It Too!" -- it's like something straight out of lies, damned lies, and statistics.