Year	Percent
1981	71.03375
1982	64.45757
1983	62.42177
1984	65.07163
1985	68.20659
1986	81.39311
1987	72.26226
1988	66.02251
1989	53.87737
1990	40.34719
1991	82.53533
1992	36.36265
1993	70.40987
1994	54.5266
1995	41.56229
1996	42.44975
1997	47.3251
1998	59.5077
1999	62.0829
2000	67.88986
2001	65.49999
2002	67.79064
2003	67.94734
2004	70.54154
2005	63.61208
2006	53.48672
2007	58.26598
2008	67.18098
2009	57.53576
2010	56.67105
2011	74.44567
2012	66.01641
2013	61.42175
2014	57.07331
2015	44.64142
2016	45.42376
2017	57.11726