Year	Percent
1991	26.67
1992	24.22
1993	23.22
1994	22.36
1995	19.58
1996	21.37
1997	22.56
1998	20.96
1999	19.34
2000	17.88
2001	18.63
2002	18.53
2003	18.87
2004	21.46
2005	22
2006	23.53
2007	21.87
2008	22.29
2009	22.43
2010	22.04
2011	21.54
2012	19.89
2013	21.15
2014	19.51
2015	18.69
2016	20.08
2017	19.21
2018	19.09
2019	18.89