Average Population Of "Keeper" Coins

I occasionally dabble in coin roll hunting and yesterday for the first time since I moved across the country I bought a $25 box of cents at my local branch. My results were nothing unusual and no real chest grabbers were present.

Of the 2500 cents in the box there were:
4 Canadian
11 Wheats (1942 through 1955 represented)
11 2009's
392 Pre-1983. (I did not separate the zinc 1982's)

This came to a 16.7% "Keeper" ratio. This is slightly lower than I would have thought. Prior boxes usually tend to be about 20% and the high I have seen in my somewhat limited (a few dozen $50 boxes and a dozen or so $25 boxes) was about 29%.

The question is here: What percentages of "Keeper" coins are people finding? I realize my chum might be your treasure but in general what kind of percentages are people seeing these days for the ones they keep?