Here are international results for Winter Bike Day. http://winterbiketoworkday.org/2013results/ Our city placed 3rd. I think our city winter cyclists fought back after not participating when this annual event started 2 years ago or so. Uh, maybe we're just cycling in winter oblivious to the rest of the world. It actually makes some interesting reading. There's a fuller statistical breakdown if you're a numbers geek...or run a bike business..
Registering online was free and of course, it is relying on people's honesty:

Over 2,000 people registered and cycled.