A simple graduated symbol map from Governing.com shows the range of commuter rates for cities – with a roll-over for specific cities to show more detail. The map for Bike Commuters shows a comparison of commuters to total workers – so each is proportional. The high margin of error in the data (which in the notes is attributed to 2006 and 2011 American Community Survey – ACS) means, as with all maps and data, one must take it with a grain of salt.
To compare, another map on the site shows total people who Bike to Work - which could be construed as the same thing, and obviously there would be some correlation – but is a specific question and not a comparison of bike commuters to overall workers, as shown above, so does make for a slightly different spread – for instance Eugene, Oregon – which is larger on the above map – is significantly smaller on the map below – because the plot is based on total riders – so obviously Portland would be bigger due to larger population.
It would be interesting to dig into some of the ACS data and see what the specific questions are, and hopefully the survey will still be around in future years (more on this to come) for future longitudinal studies.