Year	Percent
1991	33.54
1992	34.56
1993	32.87
1994	31.24
1995	29.63
1996	28.11
1997	26.64
1998	26.13
1999	23.35
2000	20.53
2001	21.9
2002	21.32
2003	22.24
2004	23.58
2005	23.2
2006	25.29
2007	26.81
2008	29.19
2009	27.22
2010	24.5
2011	21.96
2012	21.7
2013	21.01
2014	20.64
2015	20.58
2016	20.23
2017	23.43
2018	21.3
2019	22.17