Heidi Bond is also thinking about synchronicity and the extroversion-introversion divide:

While I like all my friends very much, I don’t understand how interrupting a perfectly good train of thought with the annoyance of a call could be perceived as a benefit. And I think that about sums it up—calls, however dear the friend, are an annoyance.

And so I wonder whether there’s a difference between cell phone usage of extroverts and introverts.

Undoubtably. Of course, you could be an introvert like me, but be trained to carry your phone with you all the time, and reap the worst of both worlds.

As requested in comments here, I’ve produced a map of Tennessee county growth rates; here it is in Adobe PDF format. (Once I had the code written for Mississippi it was trivial to produce one for Tennessee.)

I’m still working on a southeastern U.S. map, but it’s made much more complicated because I can’t figure out a way to toss out the Virginia independent cities, which aren’t in the map data in the maps package, from the census data in R. I may just edit the raw data file before reading it in.