The National Bureau of Economic Research’s TAXSIM model (www.nber.org/ ~taxsim/taxsim-calc8/) allows you to calculate tax liabilities for a given individual in different years. Go to this Web site and fill in the blanks to “construct” two individuals —a lower-income individual with $20,000 in income and a higher-income individual with $100,000 in income. Assume that both individuals are 45-year-old single parents of two children under age 17 who do not own homes and have no child care expenses. Use the model to calculate these individuals’ federal (effective) marginal tax rates and federal income tax liability in 1988, 1998, and 2008. Explain the pattern you find.