Year	Percent
1991	22.23
1994	22.03
1995	18.9
1996	16.62
1997	16.33
1998	17.57
1999	18.46
2000	16.36
2001	15.73
2002	14.85
2003	15.29
2004	14.04
2005	15.95
2006	13.85
2007	10.1
2008	10.44
2009	13.6
2010	14.65
2011	15.72
2012	20.58
2013	21.6
2014	20.2
2015	16.29
2016	15.23
2017	11.23
2018	8.81
2019	8.13
2020	14.19