Senator Bernie Sanders and Representative Alexandria Ocasio-Cortez have announced plans to introduce legislation that would limit the interest rate that credit card companies are allowed to charge customers. Although there is currently no federal limit, some state governments have limits. Sanders and Ocasio-Cortez propose capping the annual rate of interest on credit card debt at 15 percent. What could go wrong with this idea? Lots. Such limits, called usury laws, will make it harder for people without a good...