Year	Percent
1986	41.24796
1987	45.70408
1988	42.49825
1989	41.163
1990	44.53458
1991	48.05739
1992	53.53319
1993	50.86059
1994	51.32825
1995	49.63352
1996	49.45455
1997	46.72333
1998	43.69442
1999	45.33069
2000	41.40792
2001	40.03965
2002	39.41595
2003	40.55903
2004	39.24554
2005	37.88886
2006	46.60545
2007	47.01676
2008	44.8849
2009	45.47531
2010	44.39212
2011	45.45302
2012	43.72022
2013	45.0577
2014	43.35324
2015	45.50622
2016	41.4943
2017	40.71372