The slowest sales pace for any April in 16 years indicates the spring selling season is shaping up as a bust.

Sales of previously owned homes in April declined 0.5% from March to a seasonally adjusted, annualized rate of 4 million units, according to the National Association of Realtors. That is the slowest April pace since 2009. Sales were down 2% from April of last year. Housing economists were expecting a gain of 2.7%.

Sales of new U.S. single-family homes unexpectedly increased in April as builders lowered prices to lure buyers, but rising mortgage rates and an uncertain economic outlook remain constraints for the housing market.