Year	Percent
1980	66.97581
1981	70.69525
1982	79.18849
1983	77.80882
1984	77.7004
1985	79.18281
1986	75.44266
1987	65.73358
1988	59.49396
1989	62.21235
1990	68.81961
1991	64.3899
1992	66.65688
1993	47.0456
1994	56.51714
1995	60.3786
1996	55.29081
1997	58.53762
1998	59.08526
1999	59.99307
2000	60.51339
2001	62.35431
2002	68.54475
2003	67.40403
2004	69.563
2005	66.56648
2006	72.68449
2007	66.20683
2008	63.08841
2009	56.95978
2010	61.76803
2011	64.32991
2012	59.84534
2013	54.84665
2014	60.6853
2015	59.15865
2016	59.47999
2017	63.94257