Year	Percent
1990	32.14
1991	32.18
1992	32.21
1993	32.24
1994	32.28
1995	32.31
1996	32.34
1997	32.38
1998	32.41
1999	32.44
2000	32.48
2001	32.53
2002	32.57
2003	32.62
2004	32.67
2005	32.72
2006	32.72
2007	32.72
2008	32.72
2009	32.72
2010	32.71
2011	32.71
2012	32.71
2013	32.71
2014	32.71
2015	32.71