Year	Percent
1963	23.54372
1964	28.57576
1965	22.38309
1966	13.95993
1967	13.14431
1968	13.51356
1969	17.61803
1970	13.61655
1971	14.98321
1972	13.97145
1973	17.11251
1974	16.45752
1975	17.27725
1976	17.97476
1977	18.00521
1978	19.45808
1979	19.62053
1980	21.68644
1981	22.36789
1982	20.1634
1983	22.8018
1984	21.07541
1985	23.39771
1986	21.08192
1987	24.38071
1988	24.97842
1989	20.93482
1990	24.14845
1991	25.3476
1992	33.65565
1993	34.80835
1994	37.30228
1995	38.12679
1996	39.43312
1997	42.67395
1998	35.41824
1999	40.20945
2000	43.26339
2001	36.79004
2002	32.83822
2003	38.1646
2004	37.24747
2005	38.70116
2006	36.81749
2007	38.64108
2008	36.09927
2009	40.50575
2010	37.42616
2011	35.38899
2012	37.00842
2013	38.65685
2014	42.2442
2015	34.43233
2016	45.57438
2017	45.97088