I did an analysis about at the end of 2006 in
http://forum.treasurenet.com/index.php/topic,61685.msg443277.html#msg443277
The following is an updated post which uses my personal search totals from 2007 to get results (obviously if my numbers are not representative of the country the analysis is wrong, but it should give better perspective.)
The analysis combines my search results with pubilshed mintage figures for the various coins of interest.
My results are based upon the following analysis of my own searching where the values are (# found / # searched):
For Indian pennies: 6 / 976487
For wheat pennies: 4085 / 976487
For Pre-1941 wheat pennies: 482 / 976487
For V nickels: 1 / 352021
For Buffalo nickels: 26 / 352021
For war nickels: 229 / 352021
For pre-1960 nickels: 4462 / 352021
For Mercury dimes: 9 / 366087
For pre-1965 Roosevelt dimes: 169 / 366087
For pre-1965 Washington quarters: 13 / 105799
For Walking Liberty Half Dollars: 17 / 106370
For Franklin Half Dollars: 39 / 106370
For 90% Kennedy Half Dollars: 166 / 106370
For 40% Kennedy Half Dollars: 758 / 106370
First, here is how I arrived at my answers using wheat pennies as an example.
The total mintage of wheat pennies made: 25824458676
The total mintage of memorial pennies made: 419251676276 (assumes 2003 - 2007 were all the same as 2004)
The total mintage of lincoln pennies is then: 445076134952
Note:
The above mintages do not include all proof and mint set mintages, but since those numbers are low they will not change the overall numbers much.
So the percentage of wheat pennies if all were still in circulation is:
25824458676 / 445076134952 or approximately 5.80%
I find approximately 10.458 wheat pennies / 2500 pennies or 0.418% (per my results listed above)
That means there are 0.418% out of a possible 5.80% or approximately 7.210% are still in circulation (0.418 / 5.80 = 7.210%).
Note:
This math assumes that no other coins are circulating and mixed in. (i.e. canadian, foreign, and indian head penny mintages were ignored for this figure.)
But since other coins are mixing in the actual percentage remaining is very slightly higher.
Performing similar math for other coins gets the following results left in circulation
--------------------------------------------------------------------------------------------------
Pennies
-------
Indian Head Pennies:0.148% (2,746,124 coins)
Pre-1941 wheat pennies:3.236% (219,692,323 coins)
Wheat pennies:7.210% (1,861,915,224 coins)
Nickels
-------
V nickels:0.025% (150,080 coins)
Buffalo nickels:0.318% (3,857,617 coins)
Silver War nickels:3.815% (33,187,670 coins)
Pre-1960 jefferson nickels:18.341% (646,652,326 coins)
Dimes
-----
Mercury Dimes:0.079% (2,116,205 coins)
Pre-1965 Roosevelt Dimes:0.582% (38,501,721 coins)
Quarters
--------
Pre-1965 Washington Quarters:0.230% (8,818,229 coins)
Half Dollars
------------
Walking Liberty Half Dollars:0.160% (804,719 coins)
Franklin Half Dollars:0.346% (1,668,151 coins)
90% KennedY Half Dollars:1.465% (6,348,599 coins)
40% Kennedy Half Dollars:3.415% (28,989,386 coins)
For any other coins of interest I don't have enough, or the right, data to complete with only my search results so I didn't list them here.