That is interesting that with all the real time data capabilities such numbers are not shared more frequently.
The only thing I can guess with regards to the almost 2 decades span is 2 decades is generally considered a generation and perhaps the information was trying to convey a generational correlation?
I see the % walking inter county is no small number. Are your counties small or is it a geographical situation whereby perhaps two or more counties are butted together permitting easy crossing? (I suppose I could look that up but well that 2nd glass of wine has me in a mellow mood)
Now you make me miss Boston.
Here in ORL, they are finally moving forward with sunrail (I'm putting on my anti-flogging suit now). It's essentially a 1-line above ground S-bahn with special needs. By no means perfect, I do hope it becomes successful. There are some bike paths here but the biggy is trying to bike from A to B for 10 months out of the year, even biking up the street results in your body and clothes being completely soaked in a nasty sweat. Well at least for me. And biking on the road... Well lets just say they have a special hunting permit here for drivers which allows them to efficiently cull the biker population.
Portland is moving in the right direction by several metrics. Keep it up! It's on my list to come check out and see what's going on out there (sadly haven't been there, yet..).