Year	Percent
1990	16.72689
1991	17.60062
1992	27.79142
1993	23.0163
1994	24.90135
1995	25.47573
1996	26.28255
1997	27.98969
1998	22.86092
1999	27.70506
2000	32.71547
2001	32.95726
2002	35.2244
2003	34.54293
2004	35.63709
2005	32.90853
2006	32.06021
2007	28.41734
2008	26.25131
2009	26.54955
2010	32.56202
2011	37.04516
2012	37.46408
2013	39.74822
2014	41.19168
2015	41.01395
2016	41.33474
2017	41.44432