Year	Percent
1970	64.14144
1971	68.66473
1972	72.01202
1973	77.635
1974	80.89245
1975	85.11586
1976	95.71398
1977	93.76449
1978	90.163
1979	89.37793
1980	83.88502
1981	82.8269
1982	79.75808
1983	81.47483
1984	78.82675
1985	79.64949
1986	80.11313
1987	80.63441
1988	79.16115
1989	80.45043
1999	90.07374
2000	92.59353
2001	92.34708
2002	92.52599
2004	93.32307
2005	93.23926
2006	90.5977
2007	94.43216
2008	97.84731
2009	98.20409
2010	94.08196
2011	98.76921
2012	100.88029
2013	100.20214
2014	98.00927