Year	Percent
1971	50.9864
1972	49.1049
1973	49.9286
1974	55.45362
1975	60.38691
1976	60.56464
1977	61.63012
1978	58.721
1979	57.93569
1980	59.83749
1981	57.90533
1982	50.64662
1983	49.23885
1984	49.72394
1985	49.84031
1986	45.88469
1987	44.63452
1988	44.94501
1989	49.86577
1990	51.3712
1991	49.2591
1992	44.43289
1993	44.37923
1994	41.96003
1995	44.1214
1996	42.03915
1997	44.38413
1998	40.30126
1999	43.73956
2000	43.82822
2001	42.11815
2002	40.468
2003	45.1034
2004	48.42689
2005	46.36289
2006	48.84518
2007	50.56268
2008	47.98017
2009	42.17537
2010	41.48158
2011	44.51406
2012	45.85703
2013	43.96164
2014	41.46153
2015	41.91539
2016	41.24369