Year	Percent
1990	35
1991	34
1992	33
1993	32
1994	31
1995	30
1996	29
1997	28
1998	27
1999	26
2000	25
2001	25
2002	25
2003	25
2004	25
2005	25
2006	25
2007	25
2008	25
2009	25
2010	25
2011	25
2012	25
2013	25
2014	25
2015	25