Year	Percent
1980	68.5751
1981	75.34992
1982	70.57183
1983	65
1984	70.15173
1985	61.29572
1986	58.13035
1987	62.59266
1988	67.84694
1989	69.13121
1990	60.06537
1991	64.84968
1992	52.91925
1993	50.18441
1994	52.43821
1995	49.11101
1996	50.26588
1997	55.70716
1998	56.9277
1999	67.35425
2000	73.67147
2001	69.09935
2002	66.13037
2003	65.93645
2004	58.51347
2005	62.69395
2006	61.65052
2007	61.21539
2008	69.65297
2009	56.22321
2010	57.4719
2011	63.10407
2012	62.92999
2013	66.80209
2014	66.06358
2015	66.32536
2016	60.50553
2017	60.82699