NEW YORK (AP) ― The average roundtrip ticket within the U.S., including taxes, reached $509.15 in the first six months of this year, up nearly $14 from the same period last year. Domestic airfare continues to outpace local inflation, rising 2.7 percent compared to the 2.1 percent gain in the Consumer Price Index.

Airfare has gone up 10.7 percent in the past five years ― after adjusting for inflation ― according to an Associated Press analysis of data from the Airlines Reporting Corp., which processes ticket transactions for airlines and more than 9,400 travel agencies, including websites such as Expedia and Orbitz.

The formula for rising fares seems simple, but it eluded the airlines for years: Match the supply of seats to passenger demand.

“Airlines have reduced the number of seats while more people want to fly because of the economic recovery. All this leads to higher airfares,” says Chuck Thackston, managing director of data and analytics at Airlines Reporting Corp. “This trend in airfares is likely to continue for the near future, as the economy continues to grow.”