Year	Percent
1991	25.25
1992	25.01
1993	24.93
1994	25.01
1995	24.87
1996	25.1
1997	24.61
1998	24.02
1999	23.73
2000	24.4
2001	17.33
2002	13.96
2003	16.04
2004	15.26
2005	16.13
2006	16.71
2007	17.1
2008	15.67
2009	16.26
2010	15.63
2011	18.19
2012	18.07
2013	17.3
2014	17.79
2015	19.36
2016	19.04
2017	18.27
2018	17.63
2019	18.18