Year	Percent
1974	90.05428
1975	90.0592
1976	93.6549
1977	94.63424
1978	95.01268
1979	95.06159
1980	93.36151
1981	93.14326
1982	89.34305
1983	88.27041
1989	61.81132
1990	61.80849
1991	66.67709
1992	57.87234
1993	54.76334
1994	51.08121
1995	59.71684
1996	59.93345
1997	57.18543
1998	50.47198
1999	55.81634
2000	67.35433
2001	69.52531
2002	67.12183
2003	69.28925
2004	68.79905
2005	70.16845
2006	71.7247
2007	67.85275
2008	78.29924
2009	72.78318
2010	67.41038
2011	69.50607
2012	70.15922
2013	68.04187
2014	68.71896
2015	52.2106
2016	49.57778
2017	49.57331