Question, how many nickels and dimes are actually in circulation? The US mint website only says that coins last approximately 25 years in circulation. Can we just add up all dimes made in the past 25 years? I can't find even an estimate of the # of coins that could possibly be floating around out there. Any thoughts/links/references are appreciated!
You could only go by the actual mintage numbers of each and add them up. It would be impossible to determine which ones have fallen out of circulation, destroyed or lost forever, etc. Just say there are billions out there currently, getting an exact number you will never be able to obtain accurately.
Let me explain why I am interested in this question: I'm working on a project to document find rates of pre-1960 nickels. Me and a number of other people have documented finds in close to 1 million nickels. I have the percent probability in finding, for example, a 1939 nickel (given the # of nickels searched). I'd like to somehow estimate what % of these 1939 nickels make up the total proportion of available nickels out there in circulation, but I can't see how to do it without knowing an estimate of the total # of nickels in circulation.
All you can do is guess. No, not really since it's been done. I designed and built one based on magnets myself many, many years ago. Since then many others have copied it. It works. Here's an example of a design slightly different than my original but the concept is the same. - http://www.youtube.com/watch?v=pZb05BaRmqU&feature=player_detailpage But do me a favor, let's not get off on a discussion of this and sidetrack this thread. If you wish to discuss it let's take to the GD section.
ATT DSL service is so bad I can't even watch the uTube. Actually it's pretty easy to develop the equations to do what you want but you're shooting yourself in the feet before you start. You need data and you're throwing most of it away by not counting the later issues. There are confounding factors and I'm not going to get into them here but you just need to make the assumption that the attrition rate on all coins is the same year in and year out. If you do this you'll find about 55% of 1965 dimes are gone now and about 40% of 1965 nickels (quarters are getting close to 50%). If you live on either coast you'll need to throw out the outliers in the past ten years for dimes and 20 years for nickels because of their low velocity. The assumption that the attrition rate on the pre-1965 coinage is constant is a poor one because collectors selectively save these. You can't get an accurate rate on these because there are millions in collections and hoards. Hoards eventually get respent especially during economic downturns so the incidence of old nickels and silver dimes is inversely correlated to the health of the economy.
Just use some arbitrary number. No one can disprove it. It's like saying how big the universe is. No one can disprove whatever number they come up with. And later, if you were wrong, you just say, "oops".