A total of 85 approved bear canisters were either broken or stolen by Yosemite black bears between July 15, 2012 and July 11, 2017. During that same period, 2 Ursacks failed (1 incident was mistakenly reported twice). All of the Ursacks were older models—not IGBC approved.
This information was gleaned from a comprehensive spreadsheet of wilderness bear incidents provided to us by Yosemite. Some of the information in the report is difficult to precisely analyze because the narratives crammed into the spreadsheet are truncated. But as best we can determine, 30 approved canisters were broken enough that a bear got a food reward. Another 55 were rolled or batted away from camp and were never recovered. Many others were rolled away from camp but were eventually found.
Overall 200 bear incidents were reported. Not all involved canisters. Some of the recurring findings: bears taking backpacks with or without food inside; bears pounding canisters so that the food was inedible even if the canister remained intact; and several tales of bears getting improperly stored food because campers could not fit everything into approved containers. It is worth noting that these 200 incidents are based on reports to rangers. Many incidents go unreported.
We will ask Yosemite to post the spreadsheet because it contains fascinating and useful information, and demonstrates how hard it is to keep bears wild–especially in the heavily traveled parts of Yosemite. If you are camping in that area you need to be exceptionally vigilant.