Year	Percent
1991	20.66
1992	20.23
1993	19.73
1994	19.19
1995	18.53
1996	17.94
1997	17.19
1998	16.24
1999	15.33
2000	14.66
2001	14.17
2002	13.74
2003	13.4
2004	13.08
2005	12.68
2006	12.36
2007	11.97
2008	12.14
2009	11.98
2010	12.09
2011	12.44
2012	12.79
2013	13.14
2014	13.57
2015	13.93
2016	14.07
2017	13.92
2018	13.75
2019	13.5