We had wondered whether Seattle, which experienced a 15 percent gain in downtown ridership from 2007 to 2009, had collected 2008 numbers as well. The reason: Portland, which trended upward from 2007 to 2009, actually had a drop in rider count from 2008 to 2009, according to a preliminary report analyzed by BikePortland.org.

Seattle took a bike count in 2008, SDOT told us, but it did not include the same locations as the 2007 and 2009 counts. In 2008 the city inaugurated a city-wide survey. The 2007 and 2009 counts were for downtown ridership.

The city-wide and downtown counts are done on a rotating biennial basis. Next year (2010) will be another city-wide count, while the next commuter count won’t be till 2011.

So it’s an apples and oranges thing. But for the curious, we’re posting the 2008 city-wide bike count.

The reasons for Portland’s somewhat astonishing drop have not yet been officially published and may involve guesswork in any case. But Virginia Coffman, manager of SDOT’s bike and pedestrian program, noted that Portland’s unemployment rate is higher than Seattle’s (Bureau of Labor stats put Seattle at 9 and Portland at 10.7 percent as of October). And infrastructural saturation, a factor raised by BikePortland, may be playing a role as well, Coffman said.

We’ll look forward to publication of Portland’s official report after the first of the year.