The average price of an individual New York City taxi medallion fell to $872,000 in October, down 17 percent from a peak reached in the spring of 2013, according to an analysis of sales data. Previous figures published by the city’s Taxi and Limousine Commission — showing flat prices — appear to have been incorrect, and the commission removed them from its website after an inquiry from The New York Times.

In other big cities, medallion prices are also falling, often in conjunction with a sharp decline in sales volume. In Chicago, prices are down 17 percent. In Boston, they’re down at least 20 percent, though it’s hard to establish an exact market price because there have been only five trades since July. In Philadelphia, the taxi authority recently failed to sell any medallions at its asking price of $475,000; it will try again, at $350,000.

Most major American cities have long used a system to limit the number of operating taxicabs, typically a medallion system: Drivers must own or rent a medallion to operate a taxi, and the city issues a fixed number of them. In New York, which established its medallion system in 1937, that number is 13,437. The number has risen only gradually since the late 1990s, even as the city’s economy has boomed.