• 1970 to 1974 3
• 1975 to 1979 3
• 1980 to 1984 3
• 1985 to 1989 2
• 1990 to 1994 12
• 1995 to 1999 10
• 2000 to 2004 19
• 2005 to 2009 10
• 2010 to 2014 6
• 2015 to 2015 1