Year	Percent
1980	64.47991
1981	66.87539
1982	71.6106
1983	70.66594
1984	70.53946
1985	69.02659
1986	68.54924
1987	63.64949
1988	62.99991
1989	63.03136
1990	55.54376
1991	56.28062
1992	55.82422
1993	67.33563
1994	56.58186
1995	58.0253
1996	58.62071
1997	62.112
1998	62.67485
1999	62.97959
2000	65.38103
2001	69.42016
2002	70.59502
2003	71.33031
2004	71.91845
2005	71.78773
2006	72.58901
2007	60.95946
2008	59.77114
2009	60.18762
2010	61.16145
2011	60.60223
2012	62.16351
2013	61.82883
2014	61.23161
2015	60.51862
2016	61.0417
2017	61.27027