Year	% of total
1970	72.01293457145336
1971	79.02263943215428
1972	75.6967687502223
1973	79.56122347073088
1974	78.47810127106041
1975	76.95643825892914
1976	75.73912915114705
1977	80.66478983642227
1978	77.39097764166549
1979	76.09529719167348
1980	75.36042038352359
1981	78.31223228079348
1982	78.05502638571964
1983	78.08947780833218
1984	82.27133968946579
1985	81.50634241089702
1986	79.94217819198136
1987	76.48290545836205
1988	78.95767558676387
1989	79.16187124981758
1990	74.58595088520845
1991	72.55255255255256
1992	72.51019219569017
1993	73.5838779956427
1994	73.7441740031072
1995	74.30521696733301
1996	73.03703703703704
1997	72.4390243902439
1998	71.89605389797883
1999	71.36752136752136
2000	70.09615384615384
2001	71.1344922232388
2002	69.79264844486333
2003	71.28363475959418
2004	69.28438661710037
2005	69.9238009861049
2006	69.64997784669916
2007	70.65491183879094
2008	69.50021358393849