Year	Percent
1990	25.92569
1991	21.28693
1992	21.44755
1993	20.75783
1994	21.39523
1995	22.96052
1996	22.09465
1997	23.35937
1998	25.98203
1999	24.12448
2000	27.22895
2001	27.22985
2002	28.75822
2003	33.3913
2004	34.26482
2005	34.6097
2006	37.86399
2007	38.56459
2008	37.85699
2009	37.18445
2010	40.05513
2011	42.56317
2012	44.44359
2013	46.31983
2014	47.58721
2015	49.52089
2016	52.25985
2017	53.39253