Year	% of total
1970	96.93998638183416
1971	96.27911562934823
1972	95.22033397938729
1973	94.44087641839204
1974	92.0518374744434
1975	91.40516571208052
1976	92.21616249728285
1977	92.95393879198612
1978	92.52387175427144
1979	91.5897147937634
1980	91.06086227839607
1981	88.84146910503557
1982	87.7328203657794
1983	86.17704346252565
1984	85.57790292286555
1985	85.00639993545877
1986	88.48437016061558
1987	87.56657716644712
1988	88.04738156302534
1989	87.47479023239127
1990	96.82844077297537
1991	96.83544303797468
1992	96.87086822388717
1993	96.90615835777126
1994	96.89877121123463
1995	96.83488914819137
1996	96.73060156931125
1997	96.8092820884699
1998	96.67774086378738
1999	96.81188690132718
2000	96.97362732382187
2001	96.96632340662399
2002	96.9860064585576
2003	96.94090080708149
2004	96.88681623392992
2005	96.8475073313783
2006	96.69131014422494
2007	96.59569349212077
2008	96.58221797323135