Year	Percent
1990	16.633
1991	17.49
1992	17.87
1993	18.66
1994	17.509
1995	16.918
1996	14.818
1997	14.008
1998	14.909
1999	15.607
2000	13.663
2001	17.164
2002	20.344
2003	21.459
2004	20.481
2005	19.534
2006	15.9274
2007	17.1047
2008	18.2675
2009	22.9342
2010	19.2197
2011	15.5406
2012	14.5691
2013	15.4732
2014	16.6058
2015	16.4563
2016	17.2387
2017	17.7187