Year	Percent
1990	13.37
1991	14.22
1992	14.7
1993	15.53
1994	16.79
1995	17.61
1996	17.41
1997	17.05
1998	17.08
1999	16.7
2000	15.75
2001	14.7
2002	14.08
2003	11.56
2004	9.45
2005	9.04
2006	8.66
2007	8.29
2008	7.94
2009	7
2010	6.16
2011	5.42
2012	4.76
2013	4.18
2014	4.54
2015	4.95
2016	4.64
2017	4.36
2018	4.35
2019	4.34