Year	Percent
1990	11.26
1991	11.27
1992	9.67
1994	9.66
1995	10.18
1996	13.92
1997	12.43
1998	11.86
1999	12.25
2001	12.84
2002	13
2003	12.55
2004	13.71
2005	9.38
2006	9.39
2007	7.66
2008	8.14
2009	8.14
2010	9.82
2011	10.93
2012	10.97
2013	8.59
2014	7.14
2015	8.6
2016	7.41
2017	7.61