Year	Percent
1990	0.63251
1991	0.61249
1992	0.59342
1993	0.59576
1994	0.59201
1995	0.55057
1996	0.52921
1997	0.50783
1998	0.49181
1999	0.47657
2000	0.46553
2001	0.59698
2002	0.5808
2003	0.51028
2004	0.46693
2005	0.50616
2006	0.49071
2007	0.47537
2008	0.46116
2009	0.42727
2010	0.41602
2011	0.40511
2012	0.39463
2013	0.38449
2014	0.37458
2015	0.36492
2016	0.35549
2017	0.3724
2018	0.34654
2019	0.3537
2020	0.34738