Year	Percent
1991	19.81
1992	19.44
1993	18.87
1994	18.27
1995	17.54
1996	16.85
1997	16.29
1998	15.6
1999	14.77
2000	14.15
2001	13.56
2002	12.87
2003	12.25
2004	11.69
2005	13.25
2006	12.54
2007	13.96
2008	17.51
2009	16.72
2010	14.07
2011	13.34
2012	10.92
2013	11.61
2014	10.89
2015	11.62
2016	13.44
2017	16.55
2018	19.67
2019	23.21