It's 3 per cent annually now, and has been lower. But it's also been much higher. Many calculators will suggest 4 per cent. Assume that you'll live to age 90 RetireWeb is one Web site that has a life expectancy calculator. But that doesn't mean that the 40-year old who wants to retire at 65 should tell his calculator that he wants his money to last another 13.5 years.
Mortality tables provide the median life expectancy.
That means that half of all men who are now 40 will live beyond 78.5. Half will not make it to that age. Assume you'll make it to 90. Great news if it happens. But it does mean you'll need to save more.