illustration of Withdrawal Rates vs. Portfolio Longevity

Without comment, this is a heat scatter of constant withdrawal rates vs. portfolio longevity, where

- returns are randomized normally with a real return of .04 and a standard dev of .12
- withdrawal rates are spread out uniformly between 2 and 12 %
- a mini sim of the number of years a portfolio lasts is run 50,000 times
- "150 years" stands in here for infinity

No purpose other than to see what it looks like...