Year	Percent
1990	3.483
1991	7.817
1992	13.333
1993	17.784
1994	17.803
1995	17.7838
1996	15.5868
1997	14.7795
1998	12.882
1999	11.0021
2000	10.3495
2001	9.8597
2002	10.6558
2003	10.9584
2004	10.156
2005	8.1688
2006	7.3789
2007	6.5377
2008	6.0706
2009	8.8879
2010	9.0937
2011	8.4051
2012	8.2801
2013	8.8232
2014	9.3272
2015	9.8765
2016	9.0373
2017	8.8722