Explain the purpose of payroll taxes. Is it a proportional form of tax?

What will be an ideal response?

The payroll tax is a tax levied on the earnings from work. It is levied at a fixed percentage of the earning, and shared equally between employees and employers, the proceeds of which are earmarked to be paid into various “trust funds.” These funds, in turn, are used mainly to pay for Social Security, Medicare, and unemployment benefits.On the surface, this tax seems to be proportional, but it is actually highly regressive, for two reasons. First, only wages and salaries are subject to the tax; interest and dividends are not. Second, because Social Security benefits are subject to upper limits, earnings above a certain level are exempted from the Social Security tax. Above this limit, the marginal payroll tax rate is zero.