Maybe it's the economy.
Or maybe it's people peeved at having to pay more for off-street parking in Philadelphia.
Whatever the cause, business at city parking lots and garages has dropped since July, which is when the city increased the parking tax rate, from 15 percent to 20 percent.
"People are just not driving in to go to restaurants and for shopping," said Robert Zuritsky, president of Parkway Corp.
As head of one of the city's largest parking operators, with 50 lots and garages, he estimates that business is down seven to 10 percent.
At the same time, ridership on SEPTA is up. In fact, with rising gas prices, rail ridership in September reached its highest point in 25 years.
The change in parking practices is evident in the city's latest revenue figures.
From July through October, the parking tax generated $22 million, which means people paid a total of $109 million for off-street parking during those months.
For the same period last year, however, when the parking tax was five percent less, the city collected $17.2 million - which means off-street parking costs were higher, totaling $114 million.
"The increase in parking tax collections is no longer keeping pace with the increase in the tax rate," noted the city's fiscal watchdog, the Pennsylvania Intergovernmental Cooperation Authority, in a monthly analysis of city tax revenue released this week.
As a result, the city is running slightly behind in its projection that parking taxes will generate $68.5 million by the end of the fiscal year on June 30.
Falling short any amount would add to the city's financial crisis, as it is trying to close a $108 million deficit in the current fiscal year.
For Zuritsky, there was no surprise at the falling numbers.
"You have a recession. You have energy prices. Then, in the middle of the summer, we were forced to raise our prices because of the tax increase," he said. "It's all these things hitting at the same time."