A study recently released by the American Hotel & Lodging Association tracks data on Airbnb stays over the course of 13 months in 12 cities. Destinations included are the largest metropolitan statistical areas: New York, Chicago, Los Angeles, Philadelphia, Miami, Houston, Dallas, Phoenix, San Antonio, San Diego, San Francisco and Washington, D.C.

The study reveals nearly 30 percent of Airbnb revenue in these cities is due to rentals available year-round, with the operators managing the properties raking in an average of $140,000. These operators accounted for approximately 17 percent of the hosts located in any of the 12 cities studied. The destinations where this was seen most were New York, Miami, Los Angeles and San Francisco.

“Unfortunately, this report shows a troubling trend as a growing number of residential properties are being rented out on a full-time, commercial basis, in what amounts to an illegal hotel, and using Airbnb as a platform for dodging taxes, skirting the law and flouting health and safety standards,” says Katherine Lugar, president and CEO, American Hotel & Lodging Association.