Year	Percent
1991	17.47
1992	17.41
1993	18.26
1994	17.86
1995	17.65
1996	17
1997	17.35
1998	17.01
1999	17.94
2000	18.09
2001	15.98
2002	18.08
2003	17.58
2004	16.44
2005	15.07
2006	15.5
2007	15.47
2008	14.1
2009	13.87
2010	13.72