After 1937, the Court asked whether an activity substantially affects interstate commerce. Wickard v. Filburn (1942) added the idea that made the modern commerce power so broad: aggregation. A single farmer's wheat may not matter to the national market, but the Court looks at the total effect of everyone doing the same thing.
Why it works
Key idea
Worked example: Following Filburn's wheat
- Filburn grows extra wheat and feeds it to his chickens.
- So he does not buy that much wheat on the market.
- Multiply by many farmers: national demand for wheat falls.
- Lower demand pushes down the price that Congress's quota system was designed to raise.
Answer: Home-grown wheat affects the national market through demand. That is a substantial effect in the aggregate.
Worked example: Testing the limits of aggregation
- Wickard aggregated an economic activity: producing a commodity sold in a national market.
- In Lopez (1995) and Morrison (2000) the Court refused to aggregate noneconomic activity (gun possession, violent crime).
- In Raich (2005) it applied Wickard to another commodity grown at home.
Answer: Aggregation applies to economic activity. That limit was set decades after Wickard.
Common mistake
Supporters of Wickard say it recognizes how markets work and that Congress, accountable to voters, is the right body to regulate them. Critics, including some justices, say it removes nearly every limit on the commerce power and departs from the clause's original meaning. Justice Thomas has written separately to urge reconsidering the substantial-effects test (as in his Lopez concurrence).