Year	Percent
1990	0.54762
1991	0.49441
1992	0.48213
1993	0.45683
1994	0.43611
1995	0.60634
1996	0.59833
1997	0.51836
1998	0.53589
1999	0.52882
2000	0.53416
2001	0.51531
2002	0.5043
2003	0.49651
2004	0.49262
2005	0.48806
2006	0.46559
2007	0.37176
2008	0.3716
2009	0.37971
2010	0.38046
2011	0.37838
2012	0.38424
2013	0.38419
2014	0.38369
2015	0.36416
2016	0.34528
2017	0.3461
2018	0.34717
2019	0.32696
2020	0.33735