But the "non-motorized" numbers are slowly growing. In 2000, no city in America had more than 3 percent of its commuters getting to work by bike. Now five do. In the last decade, the share of people biking to work in 27 of the 50 largest cities increased (it declined in only two places: Mesa and Phoenix, Ariz.). More people are now walking to work than a decade ago in San Jose, Seattle, Sacramento, Atlanta, Omaha and Cleveland.
The report, based on some of the ACS questions that critics want the Census to drop, identifies some other expected patterns: The South has particularly minuscule numbers for both biking and walking to work (likely a product of both climate and sprawl). Men are more likely to bike to work than women. And those who do bike tend to leave for work later than other commuters, and they need less time to get there (19.3 minutes on average, compared with the typical 26-minute commute for most of the rest of us).
Of special interest, the demographics also reveal an important underlying dichotomy. The people most likely to bike or walk to work are either the least educated in society or the most educated. Slice the demographics by income, and the less money you have, the more likely you are to take either of these modes of transportation to work. Unless, that is, you're really wealthy. The graph below illustrates that biking and walking decline as income rises, until both start to tick back up again for the two highest income groups:
The pattern is even clearer when we look at educational attainment (this is my graph, using the Census data):
These two graphs illustrate a transportation paradox: Alternatives to driving in the United States are both a luxury for the well-off and a last resort for the poor.
In many cities, low-income workers who have no access to a car -- or only poor access to public transit -- have no choice but to walk or bike to work. And the Census data confirms that the prevalence of biking and walking steeply declines once commuters have a vehicle (or two, or three) available to them.
And yet, in other communities, developers are now building explicitly "walkable," mixed-use, urban neighborhoods where the convenience of jobs and restaurants is built into the steep price of real estate. You may have seen marketing in the Washington metro for such places, which promise that you can stroll home from work in the time that it takes to drink a latte. Increasingly, these walkable places -- which tend to be bikeable, too -- have a rent premium. They're out of reach of the very people who can't afford to own a car.
Some of the differences in educational attainment shown above reflect the high rates of biking and walking in smaller college towns such as Davis, Calif. But within a city like Washington, they also reflect the difference between residents who can afford to live downtown and those who can't afford a vehicle.