Year	Percent
1973	34.43642
1974	34.76936
1975	36.59553
1977	41.84937
1978	45.90971
1979	49.21581
1980	52.33669
1981	53.63119
1982	56.9819
1983	58.82465
1984	60.76375
1985	70.42966
1986	67.73121
1987	66.68296
1988	62.90957
1989	53.61206
1990	59.77856
1991	55.5567
1992	53.57018
1993	53.7208
1994	53.59202
1995	55.42465
1996	55.77411
1997	57.28627
1998	60.50716
1999	61.64095
2000	64.50553
2001	65.064
2002	67.24322
2003	70.08143
2004	76.94015
2005	81.48108
2006	85.57777
2007	86.34473
2008	84.71113
2009	84.02527
2010	87.75806
2011	91.51699
2012	99.37272
2013	96.29755
2014	96.82968
2015	96.86384
2016	95.26549