Year	% of total
1970	80.7164526916516
1971	80.41023042243597
1972	80.08854699156973
1973	79.07996876341389
1974	79.00908790978076
1975	79.5141140004259
1976	79.72102441663925
1977	79.29509472626425
1978	79.39330529548606
1979	78.44981782047034
1980	77.95046875333173
1981	79.27320231213872
1982	79.55783628384857
1983	79.76527551181516
1984	79.37638033244217
1985	79.28732814101681
1986	79.66408915079846
1987	79.58281310465175
1988	78.95214689149654
1989	78.36238275502699
1990	91.08554996405464
1991	91.04268719384184
1992	91.17451891174518
1993	91.62045594577943
1994	91.46191646191646
1995	90.3784477228993
1996	89.59390862944161
1997	88.38120104438643
1998	87.68441308531109
1999	87.54556500607534
2000	85.98848368522073
2001	86.31578947368422
2002	86.83274021352312
2003	87.80754510661563
2004	87.4439461883408
2005	86.97916666666666
2006	87.10045662100457
2007	88.25659596482151
2008	87.90450928381964