Year	Percent
1990	39.2405
1991	37.64871
1992	35.02335
1993	35.73301
1994	36.02778
1995	36.54564
1996	38.49812
1997	42.77334
1998	43.17091
1999	43.15565
2000	46.99416
2001	45.23535
2002	48.53609
2003	56.10426
2004	64.57909
2005	62.41767
2006	68.96897
2007	71.28458
2008	71.04741
2009	65.02148
2010	70.46895
2011	75.50477
2012	76.83128
2013	78.70357
2014	81.40925
2015	82.90992
2016	84.81667
2017	87.96194