eliminate the tax-deductibiity of health insurance benefits for people making more than $150K a year in household income, $100K for singles.
So now imagine that you're a married person with a family and you're making exactly $150K a year. Your employer pays $10K toward your health insurance. Of course, it's not subject to federal income tax, state income tax, or Social Security or HI tax. You and your spouse make a total of $150K, split roughly evenly, so both of you pay the marginal payroll tax rate of 7.65%. You also pay a marginal income tax rate of 25% and a state income tax rate of 5%. So your total marginal tax rate is 25 + 5 + 7.65 = 37.65%.
Now you earn one more dollar. What happens? That whole $10K employer contribution becomes taxable and so you pay tax on it at 37.65% or $3,765. You made an extra buck and you paid $3,765 extra in taxes. Oh, yes, plus $0.3765. So you paid $3,765.3765 in taxes. Your marginal tax rate on that dollar: 376,537.65%.