The U.S. Census Bureau released the 2014 American Community Survey numbers this morning. While several cites across the United States boast of big gains in bike commuters, the survey data shows the percentage of people riding public transportation and bikes to work in Silicon Valley California have dropped even as driving has grown.

In California’s Santa Clara County (aka “Silicon Valley”) overall, an estimated 0.6% of 145,870,653 workers biked to work for most of their journey in 2014. 27% of these bike commuters are female, compared against 47% of total workers.

Palo Alto remains the top city in the South Bay with 7.3% of workers biking to work. 43% of these cyclists are women. This 7.3%, however, continues a steady decline over the past four years in which bike commuting and transit use each have dropped by 30% since 2011. Driving, in the meantime, has grown from 69% in 2011 to 74% today.

The city of Mountain View dropped sharply from 7.6% in 2013 to 4.1% for 2014, the lowest level since 2009. Of those 4.1% of commuters, a paltry 22% are women. The numbers who report using public transportation and walking to work, however, have grown sharply. Walking increased by 31% (to 2.5% of the working population from 1.9%), while transit use grew an astounding 61% as 9.5% of Mountain View residents report riding a bus or train to work in 2014.

Sunnyvale also lost bike commuters, with 1.4% of commuters riding a bike compared against 2.2% in 2013.

Big Gain in City of Santa Clara

The city of Santa Clara is a bright spot — after years of hovering between one and two percent, 3.1% of residents say they biked to work in 2014, even as those who say they drive alone dropped from 78% to 75%. Santa Clara, unfortunately, also has the lowest percentage of women biking to work in the county — women are 11% of bike commuters.

After six years of numbers at and below one percent, San Jose managed to eke out a 1.1% figure for 2014, the highest percentage since 2008. 25% of bike commuters in “Man Jose” are women. The other modes of transportation reported in the ACS — driving, public transportation, walking, and “other” — have also remained consistent over the past four years.

For San Mateo County, 1.7% of workers biked to work in 2014, compared against 1.0% in 2013. 21% of bike commuters are female.

4.8% of workers commuted by bicycle in Santa Cruz County, a large 60% gain from 2013. Women outnumber men on bikes during the commute in Santa Cruz County; 51% of bicycle commuters are female.

Robert Prinz of Bike East Bay reports encouraging numbers for Oakland, CA.

The American Community Survey

The data above comes from the “Commuting Characteristics by Sex – 1 Year Estimates” table in the American Community Survey published by the United States Census Bureau. The 1 Year Estimates numbers are available only for communities with a population over 60,000. Depending on population size, margin of error can range from 0.1% to 2%, which means some of the gains and losses reported for the cities above are well within the margin of error. 3-year and 5-year estimates are also available eventually, but this data takes longer to compile.

The ACS asks survey respondents to report the travel mode they use most that gets them most of the way on their journey to work. If you drive part way, or bike commute twice per week, or use public transportation to get most of the way, you’re not counted as a bike commuter. I appear in these surveys, for example, as a user of public transportation. One percent in San Jose translates into a little over 5,000 people who are counted as bike commuters in that city, but the additional thousands who bring their bikes on Caltrain, light rail, and the buses are ignored.

ACS also ignores incidental trips, school trips, and recreational riding. Furthermore, ACS currently ignores those living in group residences, a fairly common living arrangement in Silicon Valley. The US Census Bureau attempts to survey undocumented immigrants and the homeless in their annual surveys, but many population experts believe the estimates from these groups are low.