Year	Percent
1990	0.59008
1991	0.58094
1992	0.55472
1993	0.51105
1994	0.49955
1995	0.50067
1996	0.52229
1997	0.4684
1998	0.44382
1999	0.43605
2000	0.42003
2001	0.39854
2002	0.36089
2003	0.35273
2004	0.40173
2005	0.39845
2006	0.35486
2007	0.34816
2008	0.34293
2009	0.34982
2010	0.34605
2011	0.34314
2012	0.34168
2013	0.33654
2014	0.35841
2015	0.34281
2016	0.33958
2017	0.35741
2018	0.35588
2019	0.34685
2020	0.35172