Propublica calculates a “true tax rate” which uses the unrealized capital gains as the denominator. They don’t make any public policy recommendation in the article, but I think computing the tax rate in this way implies that the unrealized gains should be taxable income. They also mention that Senator Ron Wyden has proposed doing this.

Why? Calculating the tax rate as “taxes paid” / “net wealth” is just what the effective wealth tax would be if one existed. This is consistent with advocating for a wealth tax, which, as I noted elsewhere, does in fact exist in other OECD countries than the US.

Wealth taxes use wealth as the denominator. Propublica uses change in wealth as the denominator.

True. I find the denominator chosen to be weird.