| 1950–1953 | 4 |
| 1954 | 5 |
| 1955 | |
| 1956–1957 | |
| 1958 | 6 |
| 1959 | 5 |
| 1960 | 6 |
| 1961 | 5 |
| 1962 | |
| 1963–1965 | 6 |
| 1966 | 5 |
| 1967 | 9 (5 from first 6, 4 from last 5) |
| 1968 | 10 (5 from both first and last 6) |
| 1969 | 9 (5 from first 6, 4 from last 5) |
| 1970 | 11 (6 from first 7, 5 from last 6) |
| 1971 | 9 (5 from first 6, 4 from last 5) |
| 1972 | 10 (5 from both first and last 6) |
| 1973–1974 | 13 (7 from first 8, 6 from last 7) |
| 1975 | 12 (6 each from first and last 7) |
| 1976 | 14 (7 from each of first and last 8) |
| 1977 | 15 (8 from first 9, 7 from last 8) |
| 1978 | 14 (7 from each of first and last 8) |
| 1979 | 8 (4 from first 7, 4 from last 8) |
| 1980 | 10 (5 from both first and last 7) |
| 1981–1990 | 11 |
| 1991–2002 | All |
| 2003–2009 | |
| 2010–2018 | |
| 2019–present | |