The top marginal income tax rate, that is, the rate paid on the 'last dollar' of the highest earner's income, was increased to 77% on the 2 millionth dollar earned during and to help finance the cost of fighting
World War I. This rate was cut over a period of 5 years following the war to a low of 25% in 1925, and tax collection as a share of output fell dramatically. In response to pressure from a now
Democratic Party-controlled Congress, President
Herbert Hoover reluctantly agreed to raise the top marginal rate to finance relief programs. In the resulting
Revenue Act of 1932 the top marginal tax rate was raised from 25% to 63%. The top marginal rate was again raised in 1936 and 1940. In 1941, the
Empire of Japan attacked the United States at Pearl Harbor. In response, the Congress declared war on Japan and
Germany and enacted an additional tax increase to help finance new war spending - raising the top marginal rate to its all-time-high of 94% on the $200,000th earned ($3.2M in 2021 dollars). Following the War, Congress reduced the top marginal rate to a low of 82.13% on the 200,000th dollar in 1949. The top marginal rate fluctuated between 70% and 92% on the 200,000th to the 400,000th dollar (the bracket on which the rate was charged was changed as well) over the following 20 years. During this time the
Social Security Act created a Social Security tax, though because the Social Security tax is capped at ~$130,000 per individual this did not add to the overall top marginal rate. Under President
John F. Kennedy the top marginal rate was decreased in the
Revenue Act of 1964 to 70%. In 1980
Ronald Reagan was elected and promised to cut the top marginal tax rate. This he did, and the top marginal tax rate was lowered over his 8 years in office from 73% to 28% on incomes over just $29,750 - the lowest this rate had been since 1925. ==After effects==