The underlying assumption to the 4% rule is that you get the average 7% growth of the US stock market. This allows for 4% withdrawal and 3% to keep up with inflation, which historically would have worked at almost all points in the US market. Firecalc [1] lets you look at how your assumptions would fare in all sequences of years of US stock data (percentage of outcomes where you would've been fine/bankrupt.)
[1] http://www.firecalc.com/