ad valorem
Many economists have argued that the sharp decline in international trade after 1930 helped to worsen the depression, especially for countries significantly dependent on foreign trade.  Most historians and economists blame the Act for worsening the depression by seriously reducing international trade and causing retaliatory tariffs in other countries. While foreign trade was a small part of overall economic activity in the U.S. and was concentrated in a few businesses like farming, it was a much larger factor in many other countries. The average ad valorem (value based) rate of duties on dutiable imports for 1921–1925 was 25.9% but under the new tariff it jumped to 50% during 1931–1935. In dollar terms, American exports declined over the next four years from about $5.2 billion in 1929 to $1.7 billion in 1933; so, not only did the physical volume of exports fall, but also the prices fell by about 1⁄3 as written. Hardest hit were farm commodities such as wheat, cotton, tobacco, and lumber.
