Year	Percent
1991	30.47
1992	30.46
1993	30.46
1994	30.3
1995	30.08
1996	29.91
1997	29.38
1998	28.75
1999	27.86
2000	27.01
2001	26.79
2002	26.8
2003	26.35
2004	25.75
2005	25.18
2006	24.94
2007	24.86
2008	25.41
2009	25.82
2010	26.01
2011	26.31
2012	26.42
2013	25.94
2014	25.16
2015	24.38
2016	24.13
2017	24.17
2018	24.38
2019	24.57