Math~
I had a couple gals that just after they were culled to the laying flock decided that they were going to eat eggs. One of the regular gals was in the nest box and one of the new gals was trying to get in there too, the regular hen wasn't going to give up her spot, but the new gal in the pen was insistant and won. The regular gal went outside in the coop run and after a few minutes of squawking she laid her egg right on the ground and the other new gal ran straight over and gobbled it up as soon as she saw it, then everyone else wondered what she was eating and helped her. I was outside the run trying to get in fast enought to kick the egg away or smash with completely into the ground with my foot and make it disappear, but I wasn't fast enough. The next day this same thing happened, but it was a different regular hen that had been in that flock for a long time, she laid her egg in the nest box and one of the new gals got right up there and pecked it and started eating it. I tossed her out of the box and cleaned it up. For a few days after that I kept finding the goo in the nest box and on the other eggs....very few eggs I might add (I think they went on a egg eating frenzy), so the next day that I had some extra time, I pulled up a 5 gal. bucket, flipped it over and planted myself on it and watched them for a while. I noticed that the regular hens would be the first in the box to lay and when one of the new girls decided they wanted to lay they would get in the same nest box (doesn't matter that there are 6 nest boxes and 5 were vaccant) anyway, as they played queen of the nest box and tried to see who master their mountain, they would crush eggs that had already been laid under them and the moment one of them noticed egg......THEY BOTH WENT TO TOWN!!!!!!!!!! Funny, I gave away the older gals in that flock and left the younger new fresh layers that were eating the eggs........haven't had an eaten egg since.
But, a couple years ago I had a couple hens that no matter what I did just couldn't be broken of egg eating...(however, I will tell you that I blew out an egg and filled it with horseradish, put in the nest box one day and it was never touched, but the real eggs that had been laid all around it were devoured.). I did end up eating those girls.....this did correct their nasty and naughty habit, but prior to this they had fair and ample time to redirect their energies and change their ways, it just didn't happen. Before I culled them, I put them in their own pen, no roosters and no other girls......they ate every egg they laid.