Took a slightly different tack on this. Went back to Dr. Broadie's ball dispersion chart for D players, scaled it down from tee shots to a 160 yard approach. The median dispersion for D players is about 7.5 degrees each way, total of 15.
A typical green might be 60 feet wide (maybe 72 with an 8' wide shoulder for mowing turns) scales out to about 4.5 degrees each side of center., or about 60% of median dispersion for bogey players. In fact, the USGA says that same 24 yards wide should accommodate 66% of bogey golfers.
But, I scaled off a few shot results from Broadie, and it seems as if about 23% of each side stays within 4.5 degrees AND goes far enough to reach the green, or perhaps 46% of total. Of course, all of this assumes dispersion patterns on approach shots is about the same as tee shots, but I believe they tend to be slightly wider off the ground than off a tee. Off the rest, based on some other stats I have seen, 23% are topped and come up short, and about 6% fly well wide of any standard sized bunker. Depending on bunker placement, and assuming one front right and front left, we can presume almost half are bunker candidates, but then, probably only half of those would find any one bunker.
That study traced 513 shots, and 48% of is about 246, and lets just say only 123 of those make a bunker. 123/513 is back to 23% overall. IF all players were D players, that might make up 7192 shots. However, D players make up about 16% of handicaps, and anecdotally, have fewer official handicaps among them, so they may make up only 33% of golfers, with C, B, and A players making up 66%. Figuring each group is proportionally more accurate (which is logically and statistically true) then over 30,000 rounds, total shots in a bunker near any given green would reduce by a third to about 2375, or 8% of shots, which you can extend out or back.
On a given day, 8% of 200 rounds might be 16 shots in the typical right front green side bunker? Seem about right?
Obviously, any bunker should be examined for position (i.e., short right is more likely to see shots) size, etc.