Great question! Complicated question... I plan to do a piece on that coming up, and I wanted to run some scenarios first. But I think striving for 10% is a great start for middle incomes, you will be able to supplement Social Security to a degree. At higher incomes I think 15-20%, as Social Security provides less % replacement. On top of having more money, a higher savings rate also means you need less income replacement since you were already spending less due to the amount being put aside. But really, save whatever you can, especially if you get a matching amount. A standard 6% deferral + 3% match gives you 9%, which is almost there! This would be net savings for retirement and not for other uses, but doesn't always have to be retirement accounts. Some people use a real estate investment approach, for example.

For low incomes, staying cash flow positive is a struggle. Any savings would be a plus.