Measuring the Shift Away From Car Ownership, City By City

A new analysis by Michael Andersen at Bike Portland helps illuminate how shifts in car ownership are playing out in different cities.

The majority of Portland's population growth consists of households with fewer cars than adults. Image: ## Portland##

Andersen reviewed Census data from 2005 and 2011. He found that households with less than one car per adult accounted for about 60 percent of Portland’s population growth. About one in four Portland households met this definition of “car-lite” in 2011, Andersen reports, compared to one in five households six years earlier.

Andersen looked at a few more cities to see whether car-lite households make up a growing share of the population.

In Austin, a more car-dependent city, not much has changed. About 13 percent of households are “car-lite,” and car-lite households account for 13 percent of the growth between 2005 and 2011. In Seattle, there’s been some movement, but not as much as in Portland: car-lite households make up 25 percent of the city overall while accounting for 37 percent of its recent growth. Meanwhile, walkable, transit-rich Boston is growing even less car-dependent: almost 70 percent of new households have fewer cars than adults, according to Andersen, compared to about half of the city’s overall population.

In Portland, Andersen notes, the real estate market is starting to react to the shift away from car-dependence — to build more walkable places and less parking. Is that going to be a trend in other American regions?

Well, car-lite households accounted for about 28 percent of America’s growth between 2005 and 2011 — double the overall national share of car-lite households.

  • Anonymous

    The method of analysis presented here — providing the % of “new” households that are (not) car dependent — seems to me to be a lot less informative than simply giving the overall % of households that are or are not car dependent, and using these figures to reason about how car dependency is changing over time. Of course, not playing games with the denominator means that the results would generally be less striking.

  • Kenny Easwaran

    Also, even if the majority of new households are car-lite, the total number of car-lite households could be decreasing if old ones add cars faster than new ones drop them.

  • Anonymous

    Actually, this effect is already folded into the value of “new” households that the report uses (hence the use of quotation marks). Unless one takes the time to work with the PUMS data for cities, the ACS can’t be used to isolate car ownership for in-movers and out-movers, so the report just uses the _net_ change in car-lite households (which includes those moving in, moving out, and those that don’t move but merely change their vehicle status).

    The fact that the study doesn’t assess the traits of an actual population of in-movers is what makes the framing so puzzling — if you’re simply measuring the net relative change of car-lite and car-heavy households, it seems pretty clear to me that the change in city-wide proportion of these households is a far more informative measure.


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