Year	Percent
1968	50.3537
1969	52.77433
1970	51.95817
1971	51.77456
1972	53.18838
1973	49.95126
1974	40.51639
1975	46.92145
1976	48.11592
1977	49.0815
1978	50.94673
1979	47.68177
1980	47.51311
1981	49.43
1982	51.71556
1983	52.51604
1984	40.03165
1985	40.76458
1986	43.54383
1987	41.05975
1988	41.05763
1989	35.43285
1990	33.4766
1991	37.26986
1992	39.30744
1993	41.84853
1994	48.51206
1995	50.1505
1996	43.62909
1997	40.34435
1998	45.80918
1999	45.77831
2000	43.08185
2001	45.97681
2002	43.25207
2003	41.52416
2004	37.27536
2005	35.07086
2006	36.34933
2007	39.35262
2008	38.79837
2009	45.91307
2010	39.03186
2011	38.63665
2012	41.51346
2013	41.69959
2014	46.82079