Year	Percent
1991	26.54
1992	25.9
1993	25.61
1994	25.41
1995	25.23
1996	24.69
1997	24.61
1998	24.42
1999	24.45
2000	24.46
2001	24.15
2002	23.9
2003	23.74
2004	23.43
2005	22.82
2006	22.46
2007	22.07
2008	22.39
2009	22.51
2010	22.26
2011	22.62
2012	23.01
2013	23.34
2014	23.69
2015	24
2016	24.19
2017	24.34
2018	24.56
2019	24.95