How many keys are lost or stolen per year?

Over a THOUSAND.

And it is rare for them to be found if they are stolen (California has more of those than any state in the U . S . A ).

How many people have keys? How many keys do they have? How many keys have been lost or stolen by/from each person and so forth. You can't know the answer, you can only guess. The bigger the sample of people you check the better the probability of your guess. I think the answer is eleven on average, but my sample space is one. The other guy thinks it is over a thousand. Who the heck knows without collecting more data.