Year	Percent
1991	10.66017
1992	10.44121
1993	10.42133
1994	10.17224
1995	9.19597
1996	8.89848
1997	9.17007
1998	8.13648
1999	7.24708
2000	6.93519
2001	6.25761
2002	6.58742
2003	6.00084
2004	5.09254
2005	4.75058
2006	4.38703
2007	4.21069
2008	3.95564
2009	3.58815
2010	3.23435
2011	3.07863
2012	3.23694
2013	3.30926
2014	3.49779
2015	3.17936
2016	2.8872
2017	2.70799
2018	2.29309
2019	2.785