What a mark-to-market tax on the very wealthy could raise
Threshold tier
Rate25%
Expected return on the stock7.0%
Avoidance / migration25%
Loss-refund drag (symmetry cost)15%
Taxable unrealized stock—
Net revenue / year—
Over 10 years—
Net revenue ≈ stock × expected return × rate × (1−avoidance) × (1−loss drag).
High-end estimates are sensitive to the avoidance elasticity — that uncertainty is the slider, not a hidden assumption.
Sources: Federal Reserve Distributional Financial Accounts (DFA) & SCF; Saez-Zucman / Realtime Inequality; Wyden Billionaires Income Tax; Treasury Greenbook. Figures illustrative — see SOURCES.md & methods.