"Compensation in the form of wages and salaries is subject to the income tax and the payroll tax. But compensation in the form of employer-provided health insurance is not subject to either.... This asymmetry tilts the playing field in favor of paying workers in insurance rather than in cash. As a result, people end up with insurance that is excessive and wages that are too low. The nation ends up spending too much on health care. The Cadillac tax helps level the playing field by curbing this subsidy for the most generous insurance plans, which do the most to drive up health costs."