Year	Percent
1990	29.56
1991	29.42
1992	29.27
1993	29.12
1994	28.98
1995	28.83
1996	28.68
1997	28.54
1998	28.39
1999	28.24
2000	28.1
2001	27.95
2002	27.8
2003	27.66
2004	27.51
2005	27.36
2006	27.22
2007	27.07
2008	26.92
2009	26.78
2010	26.63
2011	26.49
2012	26.34
2013	26.19
2014	26.05
2015	25.9