I would like to think that altitude has something to do with it, but why do no other high-altitude environments exhibit this trend? Also, I had someone check in college (since there are more high-altitude arensa), and if anything, the second halfs in high-altitude arenas are higher-scoring in college.
Also, just checked, and there were only 41 home games (as expected) in each of the 2000-2001, 2001-2002, and 2002-2003 seasons, so the overall count is high by 2 games.
Good Luck,
Bart