Year	Percent
1991	17.11
1992	17
1993	19.05
1994	21.48
1995	21.9
1996	22.25
1997	21.33
1998	21.46
1999	18.66
2000	19.22
2001	19.62
2002	20.16
2003	20.67
2004	21.12
2005	21.25
2006	21.3
2007	21.33
2008	21.34
2009	21.22
2010	22.81
2011	20.99
2012	20.89
2013	20.77
2014	22.05
2015	23.03
2016	23.31
2017	23.25
2018	23.12
2019	23.13