How did the Hawley-Smoot Tariff contribute to the Great Depression?

The Hawley-Smoot Tariff raised import duties so American jobs could be protected in farming and business, including imports. The tariff raised by 20% , which caused foreign countries to make their own tariffs against the U.S. and raising their own tariffs.

http://www.britannica.com/EBchecked/topic/550096/Smoot-Hawley-Tariff-Act