saving a years salary - what's the formula?

It depends in which country your average person lives.

Average Brits save 16.7% of their salary, so it takes them six years not counting interest earned;

Cheers, Rusty

wrote

It depends on what you consider "average". Factoring in the employee's portion of any salary deferral (ie: 401K) and any company matching contributions, and factoring in the fact that not all employers offer pension plans of any kind, we could extrapolate the number.

With a 401K where 15% of salary is put back it would take about 7 years (not counting the income gains from the investments). If you decide that only half the workers are contributing to a pension plan, you would double that to 14 years+/-. But you could reduce that some by the folks that are making after-tax savings a part of their routine, but that's not many people. So best guess, between 10 and 15 years, but I would say more than that because not all participants put back 15%.