Year	% of total
1970	80.50525246384602
1971	83.28658127934581
1972	81.2496966629049
1973	78.41073421434498
1974	82.43371268614015
1975	82.07604849255561
1976	79.53167891112138
1977	77.47020027614286
1978	76.77096372652126
1979	79.2771431517182
1980	79.05858291900174
1981	80.30622099758044
1982	80.20084815572012
1983	75.71835932697148
1984	79.38485220685772
1985	80.66939152803802
1986	79.25772210642775
1987	76.55286976707036
1988	78.09716505384289
1989	81.4463319103782
1990	78.54671280276817
1991	79.06976744186046
1992	80.73555166374781
1993	82.09219858156028
1994	83.93162393162393
1995	85.06944444444444
1996	86.11599297012302
1997	87.75862068965517
1998	88.17005545286506
1999	89.22495274102079
2000	91.00917431192661
2001	91.29662522202486
2002	91.43356643356644
2003	91.45299145299145
2004	91.91419141914191
2005	91.59663865546219
2006	91.63879598662207
2007	91.92245557350566
2008	91.9431279620853