It's 20% equivalent income tax rate if you have no conventionally taxable income. Otherwise it's 20% on top of your marginal rate. In his $100 example, you'd pay $1 in wealth tax on the $100 and $1 in tax on the $5 income earned, so your total tax is $2 on $5 of income, an effective tax rate of 40%.
But any real wealth tax is going to have exemptions, only apply to wealth above some threshold, and for the wealthy who structure their finances so as to have little or no taxable income, well they end up paying 20% like all the rest of us do.
But any real wealth tax is going to have exemptions, only apply to wealth above some threshold, and for the wealthy who structure their finances so as to have little or no taxable income, well they end up paying 20% like all the rest of us do.