Year	% of total
1970	31.813603686708134
1971	33.327448634453624
1972	34.53460155294666
1973	35.51923250989232
1974	36.49111055613133
1975	37.56560837417029
1976	38.69242461747363
1977	39.45179427195152
1978	40.23591303546014
1979	40.710861461477855
1980	41.52967538238543
1981	42.10986019291439
1982	42.74295970636552
1983	43.19443016452769
1984	44.31579278898149
1985	46.51910121251801
1986	48.56108954495998
1987	53.18329240540422
1988	53.460696935659136
1989	55.15801732134848
1990	20
1991	20
1992	20
1993	20
1994	20
1995	22.22222222222222
1996	25
1997	28.57142857142857
1998	33.33333333333333
1999	40
2000	50
2001	50
2002	50
2003	50
2004	50
2005	50
2006	50
2007	50
2008	50