Year	Percent
1990	26.77
1991	26.72
1992	26.68
1993	26.62
1994	26.55
1995	26.46
1996	26.36
1997	26.28
1998	26.38
1999	26.32
2000	26.25
2001	26.29
2002	26.28
2003	26.25
2004	26.2
2005	26.16
2006	26.15
2007	26.13
2008	26.12
2009	26.2
2010	26.13
2011	26.09
2012	26.03
2013	25.97
2014	25.88
2015	25.8
2016	25.76
2017	25.69
2018	25.64
2019	25.58