Investing - Theory, News & General • Estimating future tax rates; why not just estimate income directly?

I read the wiki article on Roth vs. Traditional and understand that the issue mainly boils down to marginal tax rate now vs. at withdrawal: https://www.bogleheads.org/wiki/Roth_vs._Traditional

I read closely through the guide to estimating withdrawal tax rates and it feels backwards to me. In both the simple and detailed methods, all you are doing is estimating the size of your investment portfolio and then applying an assumed withdrawal rate.

But if you can estimate the size of your portfolio, then assuming a withdrawal rate is just assuming your future income! The only real insight you gain is a ceiling on what a safe withdrawal amount (e.g. 4%) might look like.

Am I crazy, or would it be easier to run this calculation by just figuring out your intended withdrawal amount in dollars (by estimating expenses and applying inflation) and then making sure you are on track to save 100/4 times that?

In my case, I spend much less than I earn, so even if my expenses increase in retirement, I don't see why I would withdraw more than my current salary income. This would suggest doing traditional contributions.

But I read the wiki article on Roth vs. Traditional and understand that the issue mainly boils down to marginal tax rate now vs. at withdrawal: https://www.bogleheads.org/wiki/Roth_vs._Traditional

I read closely through the guide to estimating withdrawal taxes and feel like it didn't really answer the questions. In both the simple and detailed methods, all you are doing is estimating the size of your investment portfolio and then applying an assumed withdrawal rate.

But if you can estimate the size of your portfolio, then assuming a withdrawal rate is to just assuming your future income! The only real insight you gain is a ceiling on what a safe withdrawal amount (e.g. 4%) might look like.

Am I crazy, or would it be easier to run this calculation by just figuring out your intended withdrawal amount in dollars (by estimating expenses and applying inflation) and then double checking that this results in a sustainable withdrawal rate?

In my case, I spend much less than I earn, so even if my expenses increase in retirement, I don't see why I would withdraw more than my current salary income. This would suggest doing traditional contributions.

On the other hand, I heard on the Jill on Money podcast that in her CFP experience, heavy savers almost always end in in a higher tax bracket when they retire (thus should prefer Roth). Why might that be? Is it true to your experience?

Statistics: Posted by BogleGen2 — Thu Sep 10, 2026 12:05 am