Year	Percent
1990	15.024
1991	11.727
1992	13.527
1993	15.931
1994	13.411
1995	13.12
1996	11.147
1997	14.981
1998	12.792
1999	13.987
2000	11.855
2001	14.41
2002	17.08
2003	18.868
2004	20.724
2005	20.582
2006	17.4433
2007	17.5258
2008	18.856
2009	22.4672
2010	20.708
2011	18.9551
2012	17.8401
2013	19.6931
2014	20.2276
2015	22.1799
2016	23.5322
2017	25.6382