While the CPI is the price index with the most impact in setting interest rates, the PPI provides significant information earlier in the production process. As a starting point, interest rates have an "inflation premium" and components for risk factors. A lender will want the money paid back from a loan to at least have the same purchasing power as when loaned. The interest rate at a minimum equals the inflation rate to maintain purchasing power and this generally is based on the CPI. Changes in inflation lead to changes in interest rates and, in turn, in equity prices.