Most tax laws are not accurately indexed to inflation. Either they ignore inflation completely, or they are indexed to the consumer price index, which tends to understate real inflation. In a progressive tax system, not indexing the brackets to inflation has the effect that there is a tax increase every year, even if Congress passes no tax law. That is because an individual's income will naturally go up at the inflation rate, and the progressive taxation system causes him to pay a greater percentage of his income in taxes.