http://www.bogleheads.org/wiki/Taxation_of_Social_Security_b......

You effective retirement tax bracket could be higher than you are expecting.

Thanks for the link! I've never fully understood how SS income is taxed.

Looking at the table for married couples, I thought I would calculate a total effective tax rate with $34k of SS income and the worst case marginal tax income of $54,919.

At $34k of SS income, you would pay no taxes. HR Block tells me that you would pay a total of $8,575 on the total income of $88,900 that the table shows. If I understand correctly, I'd pay an effective tax rate of 8575/54919 = 15.6% on the $55k of income beyond SS. Above that income amount, the marginal tax rate shown in the table is 25%.

This reinforces my opinion that a traditional 401k/IRA is likely to be better tax wise than a Roth if your current marginal tax rate is 25% or higher, particularly if you expect to have little income outside of SS and investments.

OTOH, tax rates are not set in stone and it's beneficial to have a mix of Roth and traditional funds to draw from.

-murray