I think it would be a lot easier to lump people into "developed" and "developing" countries or regions of the world before talking about statistics.
I have only ever met a few people who would shrug off and spend a
Wheat cent they noticed in their change. Almost everybody I have ever asked has a jar with a few wheat cents, maybe some
State Quarters, and a couple foreign coins that were souvenirs from a trip abroad. For the US, I suspect I would be lowballing when I say 50-75% have at least one coin that they would not spend. I suspect that number would be similar for Canada, Europe, and Australia/NZ.
In China, old cash coins are believed to bring good luck and fortune, especially those of Kangxi and Qianlong. I would not be surprised if at least 30-50% of the Chinese population has at least one such coin tucked away somewhere.
I had one close Indian friend in college, and her family was not necessarily avid, but had a fair knowledge of British colonial issues, and did passively collect anything that came their way.
As far as Africa, the Middle East, and South America, I would suspect the 0.05% would be much closer--these countries generally have not churned out a numismatically significant coin since at least the 1940s, and are heavily stricken with poverty. I suspect that money there is spent and not kept, especially when saving could mean losing the value to inflation.