Okay, multiply the brackets by 30 (longer lifespans and lower long-term ROC rates). Also start with a 1% rate and round off the multipliers

Assume
0% below 30x GDP wealth
1% between 30x and 60x GDP
2% between 60x and 120x GDP
4% between 120x and 250x GDP
8% between 250x and 500x GDP
12% between 500x and 1000x GDP
16% between 2000x GDP and 4000x GDP
18% between 4000x GDP and 8000x GDP
19% between 8000x GDP and 16000x GDP
20% above 16000x GDP

The top bracket kicks in at 400M.

When the capital development of a country becomes a by-product of the activities of a casino, the job is likely to be ill-done. — John M. Keynes