Year	Percent
1991	12.62837
1992	12.15842
1993	11.8714
1994	11.0997
1995	10.81702
1996	9.54335
1997	8.33717
1998	7.23877
1999	6.25259
2000	5.40459
2001	4.83841
2002	5.25447
2003	5.18651
2004	5.10403
2005	4.73856
2006	4.2606
2007	4.38491
2008	4.23124
2009	3.92959
2010	3.79514
2011	3.82828
2012	2.91237
2013	3.10559
2014	4.43039
2015	3.99525
2016	3.64341
2017	2.52763
2018	2.16556
2019	2.4165