The U. S. federal income tax is a progressive tax. The higher the income, the higher the tax rate. Some U. S. states are still within their own jurisdictions and add a sales tax of about 7% to the price of most of the goods sold. If the sales tax is also a form of income tax, then this tax is contrary to the principle of progressiveness; the lower the income, the higher the tax rate. This passage is meant to explain:. ['In fact, the money people spend on shopping is basically the same.', "The sales tax calculation method is contrary to the government's intention to prevent the widening gap between the rich and the poor.", "Differences between federal income tax and sales tax calculations plague Americans' lives.", 'Analysis by calculation method, sales tax cannot be regarded as a type of federal income tax.']