Year	Percent
1990	41.55658
1991	42.46205
1992	39.16269
1993	47.39737
1994	47.2208
1995	47.98666
1996	48.4436
1997	45.25223
1998	45.66525
1999	46.75668
2000	52.79474
2001	54.37076
2002	52.90257
2003	52.38264
2004	54.1943
2005	55.76647
2006	56.28629
2007	56.67263
2008	55.10641
2009	57.08983
2010	55.09403
2011	55.09494
2012	56.3114
2013	54.84398
2014	53.82682
2015	53.79855
2016	53.13142
2017	54.24306