The first wave of US workers relying entirely on 401(k)s to fund their golden years is starting to retire.

For these workers and accidental investors, making a life’s saving last 20 or 30 years will be even more fraught than the saving and investing that preceded it: an investment blunder during the working years can be made up through concerted saving, but once a worker is “on batteries”, protecting capital becomes the first goal. And while 401(k) participants have been encouraged to take open-ended risks with “stocks for the long run”, they know little about investing to create maximum income at an acceptable level of risk – how to safely spend down principal.