Year	Percent
1990	12.91
1991	13.33
1992	12.94
1993	13.22
1994	13.39
1995	13.57
1996	13.85
1997	13.76
1998	13.92
1999	14.95
2000	14.68
2001	14.67
2003	17.95
2004	18.37
2005	19.68
2006	19.29
2007	20.22
2008	19.62
2009	18.63
2012	16.37
2014	17.46