From 2006 U.S. Census data, as reported at
Go Bike Boulder.

In a
survey of larger cities, Portland, OR had the highest percentage of bike commuters at 3.5 percent. Nationwide, the share of commuters biking to work in 2006 was 0.4%.
In the chart, "SOV" means Single Occupant Vehicle.
Read the complete post at http://feeds.feedburner.com/~r/Cyclelicious/~3/233921644/9-of-boulder-commuters-commute-by-bike.html