The clothing business in the US is still largely subject to what remains of the Smoot–Hawley Tariff Act, passed in 1930. Since 2001, Columbia has paired its designers with teams of trade experts in a process the company calls "tariff engineering" in order to reach lower tariffs, taxes, or duties. For example, Columbia applies a very thin layer of fabric to the soles of its shoes since tariffs on fabric soles are lower than those on rubber soles; the fabric wears away within days. For similar reasons, jackets are waterproofed and filled with at least 10% down.