NFL Referee Tendencies Across the 2006-2007 Seasons

Let's look at correlations between the distribution of statistics among the 2006 NFL referees and the 2007 NFL referees. This is a rough attempt at figuring out which particular characteristics seem to hold the following season. For example, if referees A, B, C, and D called lots of penalties in 2006 and referees E and F didn't, let's see whether the same kind of distribution exists in 2007 -- whether A, B, C, and D called lots of penalties and E and F didn't in 2007 too.

Running the numbers and checking for a correlation, some seem to hold up across the 2006 and 2007 seasons. In order of the correlation coefficient:
Average yards per penalty (0.595)
Penalties against home teams (0.489)
Penalty yards against home teams (0.417)
Total penalty yards (0.394)
Total penalties (0.392)
Penalty yards against visiting teams (0.332)
Percent penalty yards against visiting team (0.240)
Difference in yards against visiting teams (0.236)

Let's look at those with the worst correlation coefficients across two seasons:
Home team win rate (-0.172)
Points scored by home teams (-0.163)
Difference in number of penalties against visiting teams (-0.146)
Percent of penalties called against visiting teams (-0.120)