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The payroll tax — funding Social Security and Medicare — is split evenly on paper: employees pay 7.65 percent of wages and employers pay 7.65 percent. But economic research consistently finds that workers bear the majority of the combined burden. Why? Because labor supply is relatively inelastic — workers can't easily reduce how much they work — while labor demand has more elasticity. The legal 50/50 split doesn't match the economic incidence. The party that can least adjust their behavior pays the most, regardless of what the law says.
The setup
Tax incidence is the distribution of a tax's economic burden — who ultimately bears the reduction in purchasing power or profit. It is determined by one thing: the relative elasticities of supply and demand in the taxed market.
The rule: the less elastic side of the market bears the greater share of the tax burden.
The intuition: a tax creates a wedge between the price buyers pay and the price sellers receive. The side that can adjust its behavior less (the less elastic side) has fewer alternatives and therefore absorbs more of the wedge.
What happens — and why
Imagine a $1 per pack cigarette excise tax. Cigarette demand is notoriously inelastic — most smokers continue buying through moderate price increases. Cigarette supply is relatively elastic — manufacturers can adjust output and enter or exit. The inelastic buyer side bears most of the tax: retail prices rise by close to the full $1, and sales volumes fall modestly. The IRS excise tax data confirms that state cigarette tax increases translate almost directly into higher consumer prices.
Contrast this with a luxury yacht tax enacted in the United States in 1991. Wealthy buyers (elastic demand — they could buy abroad or not buy at all) bore little of the tax. American yacht manufacturers (inelastic supply — they had specialized capital and workers) bore most of it. The industry contracted sharply, and the tax was repealed in 1993.
Where you see it in the wild
The Social Security Administration's payroll tax data shows the 50/50 statutory split. Economic research — summarized in Congressional Budget Office analyses — estimates that workers bear approximately 70–80 percent of the combined employer-employee payroll tax through lower wages than they would earn without the tax.
The fix (or why it's hard to fix)
Governments cannot change economic incidence by changing statutory incidence — switching who legally pays a tax does not change who bears its economic burden. Redistributing the legal liability between buyers and sellers changes nothing about the market outcome. The only way to shift economic incidence is to change the underlying elasticities of supply and demand in the market.
