Year	Percent
1980	51.31923
1981	53.05872
1982	54.04223
1983	64.9931
1984	65.14211
1985	65.34612
1986	58.2215
1987	45.90799
1988	41.23974
1989	44.49455
1990	46.27048
1991	47.83835
1992	51.79737
1993	32.21745
1994	52.63408
1995	53.37176
1996	49.20524
1997	50.75328
1998	45.60168
1999	43.38163
2000	44.69358
2001	43.33738
2002	46.14366
2003	44.68774
2004	48.29623
2005	46.89624
2006	50.79832
2007	50.80122
2008	47.91085
2009	43.48229
2010	47.27825
2011	54.48316
2012	46.92182
2013	42.88508
2014	45.86406
2015	42.03114
2016	44.27469
2017	45.87565