Year	Percent
1991	29.02
1992	28.37
1993	27.65
1994	26.97
1995	26.33
1996	25.7
1997	25.69
1998	25.71
1999	25.7
2000	25.73
2001	25.72
2002	25.66
2003	26.84
2004	28.12
2005	27.47
2006	26.48
2007	25.35
2008	23.28
2009	23
2010	21.43
2011	20.97
2012	19.8
2013	19.85
2014	18.64
2015	18.8
2016	19.34
2017	20.53
2018	20.49
2019	21.11