Tax breaks here. Sin taxes there. They all even out apparently. Boston University economists Laurence J. Kotlikoff and David Rapson have done a little research on the subject of tax burden and have discovered that we all hover around 40% for our all-inclusive tax rate. From the richest to the poorest, we all pay roughly 40% of our income in taxes. There's a table in the linked article showing tax rate based on income and age. The highest rate is 47% and the lowest is 32% but the rates do not strictly go up with income in any age bracket. For example, those making $200,000 per year pay less in taxes than those making $150,000 or $300,000.
Now this article does come from MSN Money which has all the economic prowess of an Archie comic book so I'm going to have to do a little digging into the source to figure out how thorough the study is and if it's interpreted correctly here but it does seem reasonable on the surface. If I had to wager, I'd wager sin taxes are a big cause for the equality. We all pay the same sin tax on a $30 bottle of scotch or a pack of smokes. It just hits those making less harder. The biggest surprise I saw in the study is that the all-inclusive rate is so low. I figured that after factoring all taxes, we'd be paying at least 50% of our income in taxes but no group even breaks 50% in the study.