National data show interest rates on mortgages decreased from April to May. Contract mortgage interest rates decreased slightly from April to May—down 0.15 percent from April, according to an index of new mortgage contracts.

According to the Federal Housing Finance Agency (FHFA), the National Average Contract Mortgage Rate for the Purchase of Previously Occupied Homes by Combined Lenders index was 3.40 percent for loans closed in late May. The index is calculated using FHFA’s Monthly Interest Rate Survey. The contract rate on the composite of all mortgage loans was 3.40 percent, down 15 basis points from 3.55 in April.

Interest rates are typically locked in 30-45 days before a loan is closed. Consequently, May data reflect market rates from mid-to-late April. The effective interest rate was 3.57 percent, down 12 basis points from 3.69 percent in April. The effective interest rate accounts for the addition of initial fees and charges over the life of the mortgage.

FHFA’s interest rate survey shows the average interest rate on conventional, 30-year, fixed-rate mortgages of $417,000 or less was 3.58 in May, a decrease of 19 basis points. The average loan amount was $280,600 in May up $14,100 from $266,500 in April.

FHFA will release June index values July 30, 2013.