Year	Percent
1990	30.42
1991	30.25
1992	31.09
1993	27.98
1994	26.22
1995	25.52
1996	25.88
1997	24.96
1998	24.39
1999	24.65
2000	22.19
2001	20.92
2002	21.71
2003	21.25
2004	20.81
2005	20.37
2006	20.1
2007	20.32
2008	21.28
2009	21.26
2010	21.97
2011	20.55
2012	20.38
2013	21.26
2014	22.75
2015	23.77
2016	24.71
2017	23.43
2018	23.22
2019	21.47