Not counting the five two-year issues (1892-93 World's Columbian Exposition half dollars, 1904-05 Lewis and Clark Exposition gold dollars, 1916-17 William McKinley gold dollars, 1920-21 Pilgrim Tercentenary half dollars and 1935-36 California-Pacific International Exposition - aka "San Diego" - half dollars), there were six multi-year programs within the classic-era US commemorative series:Multi-Year Commemorative Half Dollar Programs: Coin Counts & Authorized Mintage Figures
1. 1926-1939 Oregon Trail Memorial (14 distinct coins; maximum authorized mintage: 6,000,000)
2. 1934-1938 Daniel Boone Bicentennial (16; 600,000)
3. 1934-1938 Texas Independence Centennial (13; 1,500,000)
4. 1935-1939 Arkansas Statehood Centennial (15; 500,000)
5. 1946-1951 Booker T. Washington Memorial (18; 5,000,000)
6. 1951-1954 George Washington Carver-Booker T. Washington Memorial (12; <5,000,000*)* Note: A maximum mintage for the George Washington Carver - Booker T. Washington half dollar was not specified in its authorizing legislation. The coin's maximum mintage was to be calculated based on the total number of coins authorized for the BTW program minus BTW coins already struck/distributed plus BTW coins returned to the Mint for melting. Combined, the mintage for the two programs could not exceed five million coins but there was no legislated mintage split between them.
More than any other coins of the series, these generally exploitative, multi-year programs were the driver behind the demise of the classic series. Collectors grew tired of the way these programs were manipulated by coin sponsors and their dealer partners, the artificial rarities that dealers created to support their charging of grossly inflated prices for some of the individual issues and the fact that the coins were being issued year-after-year with the same design and, generally, in years without any connection to the original person/event being commemorated.
Adding up the individual maximum authorized mintage figures, the overall total amounts to 13,600,000 potential commemorative half dollars across the multi-year coin programs listed. In actuality, the net total mintage for the group is 3,466,685 coins - just 25.5% of the authorized limit. (None of the programs came close to selling out their total authorized limit.)
It's quite clear from the sales figures that collectors grew weary of the multi-year issues and did not pursue sets of them to the same degree as individual types - the same as today. While such a difference in sales figures is to be expected, the chasm between "what could have been" and "what happened" is great enough to draw reliable conclusions (IMO) about the disparity between "Type" and "Complete Set" pursuits - collector backlash, fatigue and budget busting being chief among them. Multi-Year Commemorative Half Dollar Programs: Net Mintage Figures
1. 1926-1939 Oregon Trail Memorial - 203,102 (~3.4% of authorized maximum)
2. 1934-1938 Daniel Boone Bicentennial - 87,187 (~14.5%)
3. 1934-1938 Texas Independence Centennial - 149,661 (~10.0%)
4. 1935-1939 Arkansas Statehood Centennial - 85,302 (~17.0%)
5. 1946-1951 Booker T. Washington Memorial - 1,609,041 (~32.2%)
6. 1951-1954 George Washington Carver-Booker T. Washington Memorial - 1,332,192 (~39.3%*)* Note: The percentage uses the balance of the BTW mintage (3,390,059) as its denominator.
I'm a Type collector, having one nice example of each of the above is fine for me. Some collectors pursue complete sets of these issues and form attractive collections - more power to them! We each need to pursue our own collecting path!
If you'd like to read more about any of the coins/programs listed above, check out: Commems Collection.
I've previously posted about each of them!