You can search for "the 4 percent rule" or "trinity study" if you're curious about more. But basically, stock markets over long time average 7-8%. Subtracting i

You can search for "the 4 percent rule" or "trinity study" if you're curious about more. But basically, stock markets over long time average 7-8%. Subtracting inflation gives you a rule of thumb of 4% that historically would have worked. Of course, the future might not match. But the studies also use a fixed withdrawal rate throughout. One could further mitigate the risk by having a small side-income some years, reducing spending in down-years etc. Also, how much money one needs post-retirement is often less, for instance if the mortgage is paid down, not housing kids any more etc.