Year	Percent
1970	24.18821
1971	27.55152
1972	27.86098
1973	29.93709
1977	31.86908
1978	31.6844
1979	27.88516
1980	30.36014
1982	27.59557
1983	27.64131
1984	25.49089
1985	26.5666
1986	32.97165
1987	40.87414
1988	40.84549
1993	44.12847
1994	49.63845
1995	45.65475
1999	63.56463
2000	61.4092
2001	62.02814
2002	70.6317
2003	71.25578
2004	72.866
2005	77.06057
2006	76.95676
2007	77.10375
2008	76.07676
2010	81.62555