Year	Percent
1991	26.11
1992	26.16
1993	26.22
1994	26.16
1995	25.15
1996	24.53
1997	24.44
1998	24.64
1999	25.44
2000	25.58
2001	26.4
2002	26.49
2003	25.61
2004	24.8
2005	24.39
2006	24.18
2007	23.8
2008	23.55
2009	24.24
2010	24.4
2011	23.77
2012	23.15
2013	22.7
2014	22.16
2015	21.63
2016	21.65
2017	22.09
2018	22.25
2019	22.14