Year	% of total
1970	74.71515526423799
1971	77.66295052013938
1972	76.9118483361828
1973	78.53522259102415
1974	78.26099071693598
1975	77.56076107731403
1976	76.61376062537599
1977	78.39982281010461
1978	76.97110951826414
1979	76.1845003547163
1980	75.8127545186256
1981	76.24706648017458
1982	75.80399896104623
1983	74.69835956701073
1984	75.10873171058127
1985	74.18627174125697
1986	73.10495343843915
1987	71.6989877442436
1988	73.15070991662763
1989	73.44438898174384
1990	73.03664921465969
1991	72.28327228327228
1992	72.01850582590815
1993	71.79616548940464
1994	71.5959729328272
1995	71.1311475409836
1996	70.86830213040672
1997	70.04048582995951
1998	69.67999999999999
1999	68.3066361556064
2000	68.02644308287648
2001	67.68552071844967
2002	66.97319201995012
2003	66.70726137920536
2004	66.30288533413065
2005	65.97953433189974
2006	64.89143192488262
2007	64.54273929739725
2008	63.72288313505948