Year	Percent
1990	15.07
1991	15.3
1992	15.2
1993	15.15
1994	14.96
1995	14.93
1996	14.86
1997	14.82
1998	14.8
1999	14.63
2000	14.42
2001	14.25
2002	13.96
2003	13.62
2004	13.31
2005	13.02
2006	12.53
2007	12.08
2008	11.64
2009	11.31
2010	10.95
2011	10.7
2012	10.51
2013	10.34
2014	10.12
2015	9.88
2016	9.72
2017	9.54
2018	9.29
2019	9.08