Of course wealthy people make up the bulk of the total income tax payments. Even a constant tax rate would result in the wealthy making up the bulk of the payments. Take a simple example of two people, both taxed at 15%. One makes 100 (pays 15 in taxes) and the other 1000 (pays 150 in taxes). Of the total taxes (165), the rich person pays ~90%, yet they are both taxed at the same rate.