The article examines the causes of credit crunches in the U.S. economy over different time periods. It uses a theoretical model to show how interest rates and bank capitalization affect lending. The recent subprime-mortgage crisis led to a global credit crunch, making it harder for people and businesses to borrow money. Historical examples like the Great Depression and the 1974 oil crisis show how supply side disturbances can trigger credit crunches. The study highlights the impact of central bank dysfunction and market disruptions on lending conditions.