Year	Percent
1987	48.94095
1988	46.63127
1989	44.94687
1990	32.20888
1991	35.14987
1992	42.83155
1993	43.2957
1994	44.0906
1995	48.29261
1996	52.4972
1997	54.99938
1998	47.93453
1999	52.33093
2000	62.92932
2001	66.21906
2002	68.71808
2003	69.56209
2004	73.79488
2005	68.41292
2006	67.68907
2007	62.97932
2008	62.53982
2009	54.97373
2010	67.016
2011	75.67271
2012	74.59183
2013	72.73137
2014	73.95645
2015	73.33799
2016	73.52902
2017	73.69808