Interval              MPECS Discovery Observations
1931-1935                  0         0           61
1936-1940                  0         0            0
1941-1945                  0         0            0
1946-1950                  0         0            0
1951-1955                  0         0            0
1956-1960                  0         0            0
1961-1965                  0         0            0
1966-1970                  0         0            0
1971-1975                  0         0            0
1976-1980                  0         0            0
1981-1985                  0         0            0
1986-1990                  0         0            0
1991-1995                  0         0            0
1996-2000                  0         0            0
2001-2005                  0         0            0
2006-2010                  0         0            0
2011-2015                  0         0            0
2016-2020                  0         0            0
2021                       2         0            0