Year	Percent
1971	13.00497
1972	16.3171
1976	22.8646
1978	30.73464
1979	31.82096
1980	33.19535
1981	31.17652
1982	30.65824
1983	30.17864
1984	25.3918
1985	20.02618
1986	20.56595
1987	19.49421
1988	24.00962
1989	18.63216
1990	22.93684
1991	23.27737
1992	24.04374
1994	18.67077
1995	26.2117
1996	30.12938
1999	39.80852
2000	48.34584
2001	55.52132
2003	59.43255
2004	62.23191
2005	62.0547
2006	62.31121
2008	55.83536
2009	55.83493
2010	61.12228
2011	63.0155
2012	66.75051
2013	71.39438
2014	77.7736
2015	78.49955