Year	% of total
1970	78.076353897506
1971	79.15676012289234
1972	75.79487080275939
1973	78.36533122217932
1974	79.28344040230245
1975	79.28965947594749
1976	77.91040843174024
1977	77.96468610234295
1978	78.47495178039998
1979	78.57766186141876
1980	78.62980743304956
1981	78.18427299115451
1982	78.10659503640285
1983	78.75217910943616
1984	78.60839483642083
1985	77.94706505765238
1986	76.59880429114843
1987	76.61395638990521
1988	74.77022465443073
1989	74.11640660099766
1990	45.45454545454545
1991	43.46153846153846
1992	46.54178674351585
1993	51.264755480607086
1994	61.58940397350994
1995	56.65024630541872
1996	55.58441558441558
1997	53.385416666666664
1998	58.082191780821915
1999	61.47308781869688
2000	62.01117318435754
2001	61.03542234332425
2002	61.29032258064516
2003	64.34540389972145
2004	60.4221635883905
2005	64.13043478260869
2006	65.24064171122996
2007	66.57894736842105
2008	67.60925449871465