There's an old saying -- I've heard it ascribed to FDR adviser Harry Hopkins -- that while tax policy often amounts to "robbing Peter in order to pay Paul," the person who does it can usually count on Paul's vote.

Which is an especially good deal if Peter doesn't vote at all. 

One way of looking at Mayor Luke Ravenstahl's proposal to tax college students is this: It's robbing the crowd at Peter's Pub  to pay the rest of Pittsburgh. And that's a politically viable idea because -- surprise, surprise -- college kids don't pay attention. 

To prove it, I took a look at nearly a dozen voting precincts in the city where at least 80 percent of the residents are between 18 and 39 years old. (I'm working from US Census data compiled by PA Voice, a project that tries to turn out young voters and others who historically don't show up at the polls much.) These precincts are concentrated largely in Oakland, Shadyside, and the areas around Duquesne University. And for the most part, these are the places where -- during the 2008 election -- students turned out in droves to vote for Barack Obama. 

The results this time were less than encouraging. 

Take Ward 4, District 8. This is central Oakland, home to a bunch of dorm housing. According to Census figures, nearly every single person -- 99.3 percent -- living in this area is between the ages of 18 and 39. In 2008, turnout in this district was just under half (48.5 percent).

What was it last week? A whopping 2.33 percent. 

Now granted, turnout was down across the county -- across the country. And Barack Obama's history-making campaign generated a huge amount of interest last year -- especially among the young. But this year's turnout was dismal even compared to the showing in 2007. A stunning 3.66 percent of voters turned out in Ward 4, District 8 two years ago. 

And so it has been across the board. In the 11 precincts I looked at, voting turnout averaged 13.95 percent. That's down from just under 57 percent in the 2008 Presidential election ... and even slightly lower than the 18.45 percent posted in 2007.

Now there are all kinds of caveats with this data, of course. I'm using Census data -- and nearly decade-old Census data at that -- to establish the number of young residents. But I'm using county voter-registration data to determine turnout ... and some of those folks no doubt moved away since 2008.

So this is a crude measure at best. But I think it offers some rough data to support what everybody already knows: College kids don't vote in municipal elections, and politicians can safely blow them off. 

Which is too bad for the two guys who ran against Ravenstahl. In Ward 4, district 8, indepenent challengers Kevin Acklin and Dok Harris both beat Ravenstahl by nearly two-to-one margins.  The mayor got 17 votes, while Acklin got 33 and Harris -- whose campaign HQ was on S. Craig Street -- got 32. 

The total number of voters registered to vote in this district? 3,610. 

So there's the (admittedly remedial) lesson in electoral math.