[kulkarnic]

You only pay capital gains taxes when you realize gains, not every year.

Trump would pay 15% of $20B = ~$3B, so his net worth would be $17B. And this is assuming that his stock investments don't pay qualified dividends that are reinvested. So, yeah, he'd have much more than $12B.

[Agathos]

If you buy a stock and hold it, you don't have to pay capital gains along the way. But if you buy a mutual fund and hold it, capital gains will pass through to you whenever the manager sells stocks to adjust the portfolio. There are "tax efficient" mutual funds whose mission is to minimize that churn, but no fund can keep it at zero. I don't know how many tax efficient mutual fund options there were in 1982.