Year	Percent
1991	24.15
1992	24.29
1993	22.72
1994	23.1
1995	23.41
1996	24.19
1997	23.97
1998	23.57
1999	27.56
2000	23.92
2001	20.91
2002	23.2
2003	22.69
2004	23.37
2005	22.9
2006	23.65
2007	24.97
2008	25.77
2009	25.75
2010	26.01
2011	23.44
2012	22.13
2013	23.05
2014	23.14
2015	21.27
2016	21
2017	19.48
2018	18.03
2019	17.92