Unless you haven’t been paying attention to politics for the past few months, you know by now that former Massachusetts governor Mitt Romney is very wealthy.

But, how does Romney’s wealth — as translated in the political conversation through his tax returns — compare to that of the last few presidents? Thanks to the Sunlight Foundation, the Fix’s new favorite site, we know.

The chart below shows both the year-by-year incomes of and the effective tax rate paid by Romney as well as the last five presidents (including Obama).

The results speak to why Romney wants to talk as little as possible about his tax returns (and, more broadly, his wealth) while President Obama’s campaign wants to bring it up as much as possible.

Romney’s earnings are by far the highest and his tax rate is the lowest of any of the individuals measured in the chart. As Sunlight’s Lee Drutman writes: “The reason is pretty straightforward. Romney’s income primarily comes from investments, and the resulting capital gains are taxed at a rate of 15 percent.”

It’s also worth noting that all of the tax returns with the exception of Romney are from sitting presidents, making it something slightly short of an apples to apples comparison.

Again, though the chart above speaks to the fact that Romney’s wealth is not a legal problem but a political one. No one — not even Democrats — claim that Romney did anything untoward in his tax returns. Rather, they believe that his immense wealth and the exoticness with which it is managed and maintained puts him at a remove from the lives of most average Americans.

It’s why Democrats won’t give up pushing for the release of more tax returns and why Romney, almost certainly, will release as little new information about his wealth as is possible to effectively squelch the story.