Year	Percent
1990	11.98
1991	12.85
1992	12.09
1993	11.36
1994	10.68
1995	10.03
1996	9.42
1997	8.84
1998	8.29
1999	7.77
2000	7.27
2001	6.81
2002	6.73
2003	6.99
2004	7.56
2005	7.01
2006	6.81
2007	5.25
2008	5.93
2009	6.35
2010	5.44
2011	5.46
2012	4.95
2013	3.91
2014	3.17
2015	3.28
2016	2.86
2017	2.76
2018	2.94
2019	3.48