Year	Percent
1990	24.17531
1991	32.64213
1992	35.93014
1993	32.70197
1994	29.70996
1995	40.03683
1996	39.57692
1997	39.72346
1998	43.2982
1999	46.33251
2000	48.93762
2001	44.87878
2002	45.54576
2003	46.58859
2004	45.55819
2005	48.14781
2006	48.06621
2007	49.39512
2008	46.48741
2009	47.79771
2010	46.21464
2011	42.92461
2012	50.51344
2013	50.43496
2014	52.24322
2015	53.78879
2016	55.42132
2017	56.17236