Myth: Massive Tax Cuts Pay for Themselves by Increasing Government Revenue

The Laffer Curve is a real economic concept with a narrow, uncontroversial claim at its core: if the tax rate is 0%, the government collects no revenue because it taxes nothing; if the tax rate is 100%, the government also collects no revenue because no one has any incentive to earn income. Somewhere between those two extremes lies a rate that maximizes revenue. The problem is not the concept itself — it is the leap from that observation to the policy prescription that current U.S. tax rates are above the revenue-maximizing peak and that cuts will therefore pay for themselves. Most rigorous economic research places the revenue-maximizing top marginal rate somewhere between 60% and 70%, which is far above the current 37% top rate. Cutting rates from 37% moves the tax code further away from that peak, not closer to it.

Reagan's 1981 Economic Recovery Tax Act is the foundational case study for supply-side theory, and the actual record is not encouraging. The top marginal rate was slashed from 70% to 50% in 1981 and then to 28% by 1986. Federal revenues, adjusted for inflation, fell in 1982 and 1983. The federal deficit, which was roughly $79 billion when Reagan took office, swelled to over $220 billion by 1986 — a tripling of the deficit in nominal terms. To patch the revenue shortfall, Congress passed tax increases in 1982, 1983, and 1984, which supply-side advocates rarely mention. The Reagan era demonstrated that even under favorable conditions — a large rate reduction, a recovering economy — tax cuts did not come close to generating enough growth to offset lost revenue.

The Bush tax cuts of 2001 and 2003 repeated the pattern on a larger scale. The Congressional Budget Office projected at the time that the cuts would cost approximately $2.5 trillion over ten years, and follow-up analyses confirmed those estimates were roughly accurate. The economy did grow in the mid-2000s, but that growth was driven primarily by a debt-fueled housing bubble rather than by the productivity and investment gains supply-side theory predicts. When the financial crisis hit in 2008, the revenue base collapsed, and the country entered the Great Recession with a structural deficit that the tax cuts had made substantially worse. The CBO and Tax Policy Center both found that the Bush cuts were the single largest contributor to the fiscal deterioration of the 2000s, responsible for roughly one-third of the swing from surplus to deficit.

Kansas conducted what Governor Sam Brownback himself called a 'real-time experiment' in supply-side economics beginning in 2012. The state eliminated income taxes on pass-through business income and sharply cut individual rates, expecting a surge of economic activity to replenish revenues. Instead, state revenue fell by hundreds of millions of dollars annually, forcing deep cuts to education, infrastructure, and public services. Kansas's economic growth actually lagged neighboring states during the experiment, the opposite of what the theory predicted. By 2017, the Republican-controlled state legislature voted to reverse the cuts — overriding Brownback's veto — because the fiscal damage was unsustainable. The Kansas episode is the closest thing economics has to a controlled experiment on supply-side theory, and the result was an unambiguous failure.

The 2017 Tax Cuts and Jobs Act is the most recent large-scale test. The CBO projected it would add approximately $1.9 trillion to the federal deficit over ten years, even accounting for some economic growth effects. Proponents predicted a wave of business investment driven by the corporate rate cut from 35% to 21%. Corporate investment did tick upward in 2018, but the effect was modest, short-lived, and consistent with normal business cycle variation rather than a structural shift. Much of the corporate tax savings went to stock buybacks rather than new capital investment or wage increases. The 'dynamic scoring' models used to justify the bill projected GDP growth of 0.7% to 1.0% above baseline — projections that independent economists described as optimistic and that have not materialized in the years since passage. The federal debt has continued to rise on the trajectory the CBO predicted.