http://www.huduser.org/portal/sustai..._072512_1.html
Elements That Influence Bike Commuting
Cyclists ride in the dedicated Pennsylvania Avenue Cycletrack in Washington, DC Nevertheless, the study found that cities with more bike paths and lanes, on-street lanes, and off-street paths have higher rates of bike commuters. Other findings included:
Of the 90 U.S. cities included in the study, Portland, Madison, Minneapolis, Boise, and Seattle had the highest percentages of bike commuters.
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and here is a study, the link is referenced in the above article.
http://policy.rutgers.edu/faculty/pucher/bikepaths.pdf
Rank % of commuters by bike
1 Portland, OR
2 Madison, WI
3 Minneapolis, MN
4 Boise, ID
5 Seattle, WA
6 San Francisco, CA
7 Sacramento, CA
8 Washington, DC
9 Oakland, CA
10 Tucson, AZ