Year	Percent
1990	19.2
1991	18.86
1992	17.48
1993	16.16
1994	14.86
1995	13.58
1996	12.42
1997	11.28
1998	10.22
1999	9.26
2000	8.39
2001	7.58
2002	7.52
2003	7.49
2004	7.46
2005	7.44
2006	7.39
2007	7.36
2008	7.36
2009	7.37
2010	7.38
2011	7.39
2012	7.4
2013	7.42
2014	7.45
2015	7.48
2016	7.54
2017	7.6
2018	13.84
2019	11.97