The tariffs initially appeared to be a success; according to historian Robert Sobel, "Factory payrolls, construction contracts, and industrial production all increased sharply." However, larger economic problems loomed in the guise of weak banks. When the Creditanstalt of Austria failed in 1931, the global deficiencies of the Smoot–Hawley Tariff became apparent.[12]

U.S. imports decreased 66% from $4.4 billion (1929) to $1.5 billion (1933), and exports decreased 61% from $5.4 billion to $2.1 billion. US gross national product fell from $103.1 billion in 1929 to $75.8 billion in 1931 and bottomed out at $55.6 billion in 1933.[21] Imports from Europe decreased from a 1929 high of $1.3 billion, to $390 million in 1932. U.S. exports to Europe decreased from $2.3 billion in 1929 to $784 million in 1932. Overall, world trade decreased by some 66% between 1929 and 1934.[22]

Unemployment was 8% in 1930 when the Smoot–Hawley Act was passed but the new law failed to lower it. The rate jumped to 16% in 1931 and to 25% in 1932–1933.[23] There is some contention about whether this can necessarily be attributed to the tariff.[24][25] The Great Depression was already in motion before Smoot-Hawley, mainly due to financial instability, falling demand, and poor banking practices. However, the tariff worsened the crisis by shrinking global trade, hurting farmers, and reducing employment in export-dependent industries. Had it not passed, the Depression still would have occurred, but perhaps with less severity.