(MC)The timeline below shows changes in U.S. tariff policy between 1920 and 1930:
• May 1921 - Emergency Tariff increases import taxes on agricultural products
• September 1922- Fordney-McCumber Tariff raises tariffs on farm and manufactured goods
• June 1930- Smoot-Hawley Tariff increases tariff levels to record high level
What conclusion can be drawn from this timeline?
The American economy was almost entirely self-sufficient throughout the 1920s.
During the 1920s, Congress supported domestic producers with a protective trade policy.
During the 1920s, the United States shifted from an export-based economy to an import-based economy.
Crop prices and corporate profits increased steadily during the 1920s as a result of government policy.

We can infer from the information in the question that during the 1920s, and even in 1930, Congress passed several laws that aimed at protecting American domestic producers from foreign competition.

These protectionist laws were the tariffs that are listed in the question. A tariff is simply a tax on foreign goods, and are the most commonly used protectionist policy.