Sales of previously occupied U.S. homes slowed in March, a sluggish start to the spring homebuying season as elevated mortgage rates and rising prices discouraged prospective home shoppers.

Existing home sales fell 5.9% last month from February to a seasonally adjusted annual rate of 4.02 million units, the National Association of Realtors said Thursday.

Sales fell 2.4% compared with March last year. The latest home sales fell short of the 4.12 million pace economists were expecting, according to FactSet.

The average cost of a U.S. mortgage, which climbed to its highest level in two months last week, is a significant barrier for would-be homebuyers, said Lawrence Yun, NAR’s chief economist.

“Residential housing mobility, currently at historical lows, signals the troublesome possibility of less economic mobility for society,” Yun said.

Home prices increased on an annual basis for the 21st consecutive month, although at a slower rate. The national median sales price rose 2.7% in March from a year earlier to $403,700, an all-time high for March.

There were 1.33 million unsold homes at the end of last month, an 8.1% increase from February, NAR said.

That translates to a 4-month supply at the current sales pace, up from a 3.2-month pace at the end of March last year. Traditionally, a 5- to 6-month supply is considered a balanced market between buyers and sellers.