The seemingly unrelenting string of positive monthly home sales data finally came to an end last month as buying activity fell short compared to the same time a year earlier.

Single-family home sales fell 7.3 percent in May, the first significant decline in three years, the Houston Association of Realtors reported Wednesday.

The group attributed the decline to this area’s lack of housing inventory.

“It was just a matter of time before our depleted supply of inventory caught up with us,” Chaille Ralph, the association’s chairwoman, said in a statement. “This is Economics 101: Supply and Demand. Until more homes are listed for sale and new housing is built, it’s a safe bet that there will be further sales declines and more demand for rental properties.”

Month-end pending sales for all property types totaled 4,922, a 3.8 percent decline versus last year, signaling another decline when the June numbers are tallied. The number of available properties at the end of May fell 10.9 percent to 28,712, according to the data, which is based on sales handled through the association’s Multiple Listing Service in primarily Harris, Fort Bend and Montgomery counties.

With for-sale homes hard to come by, the single-family rental market continued to flourish in May. Home rentals shot up 20.4 percent compared to a year ago. The average rent for a single-family home increased 4.5 percent to $1,727 per month.

A 10 percent increase in sales of homes that sold for more than $500,000 helped nudge the median sales price higher last month to a record $200,000, a 6.4 percent increase over a year earlier.

The low levels of housing stock have been pushing up prices, as buyers continue to enter into bidding wars and offer more than sellers are asking in order to win a home in today’s competitive market. Homes stayed on the market an average of 50 days last month, down from 60 days during the previous month and the lowest number on record.

Months inventory — the amount of time it would take to sell all the homes on the market based on the previous 12 months of sales activity — ticked up to a 2.8-month supply after holding steady at 2.6 months from December through April.

Buyers closed on 7,145 single-family homes last month. It was the market’s first major decline since May 2011.

May townhouse and condominium sales rose 4.8 percent from a year earlier. The median price increased 2.7 percent to $143,750, while inventory fell to a 2.6-month supply.