Year	% of total
1970	85.84138644863536
1971	84.50536638873932
1972	84.04802300777465
1973	83.99947987684534
1974	84.6707847031047
1975	84.58106947491183
1976	84.23863864031252
1977	84.3822990352448
1978	83.92666640669847
1979	82.59004681590861
1980	80.36933517711918
1981	80.0549848515939
1982	80.80729322204975
1983	77.94723573555223
1984	78.79916043751454
1985	78.44406218783453
1986	76.08067490802736
1987	73.98708598978368
1988	74.82717821608003
1989	77.67416086700769
1990	83.50340136054422
1991	79.95910020449898
1992	81.27340823970037
1993	82.71186440677965
1994	82.68907563025209
1995	79.32330827067669
1996	77.62906309751433
1997	77.99295774647888
1998	76.47058823529412
1999	78.5824345146379
2000	78.33827893175074
2001	77.94117647058823
2002	77.92207792207793
2003	78.54195323246216
2004	77.40112994350282
2005	77.94316644113667
2006	78.01608579088472
2007	77.80748663101605
2008	77.58620689655173