Generally, private lenders require borrowers with down payments of less than 20 percent to purchase private mortgage insurance. However, mortgage insurance does not protect the borrower. The Federal Housing Administration (FHA) insures lenders against losses incurred when borrowers default on their home loans. However, because the FHA insured nearly 30 percent of all single-family loans—higher than the 10 percent share considered optimal by government officials—the FHA is tightening its requirements for borrowers with small down payments.