Year	% of total
1970	51.72909683077268
1971	51.95433446398248
1972	52.03285873094183
1973	52.3994796425896
1974	52.59047398139539
1975	53.20247379064743
1976	54.19995540061141
1977	54.604849145476486
1978	54.99462598270396
1979	55.53168157896601
1980	56.301501934486495
1981	57.14848928333666
1982	58.30055265626507
1983	59.50013873850989
1984	60.258459077218276
1985	60.915890388173246
1986	61.46435933836217
1987	61.498988677586276
1988	62.2527902557544
1989	62.32974266935943
1990	25
1991	47.05882352941176
1992	54.54545454545454
1993	62.96296296296296
1994	68.75
1995	70.27027027027027
1996	94.11764705882352
1997	96.43916913946587
1998	97.5359342915811
1999	98.11616954474097
2000	98.34815756035579
2001	98.56704196519959
2002	98.79931389365352
2003	98.89380530973452
2004	99.02912621359224
2005	99.13494809688581
2006	99.06432748538012
2007	99.05044510385757
2008	99.03614457831326