Year	Percent
1990	0.48367
1991	0.4608
1992	0.4475
1993	0.43497
1994	0.41144
1995	0.57376
1996	0.56239
1997	0.55808
1998	0.56695
1999	0.52462
2000	0.49822
2001	0.49467
2002	0.48023
2003	0.46983
2004	0.44376
2005	0.43576
2006	0.42669
2007	0.4174
2008	0.40812
2009	0.44524
2010	0.43459
2011	0.41909
2012	0.41297
2013	0.40574
2014	0.39237
2015	0.3883
2016	0.37823
2017	0.35602
2018	0.35011
2019	0.34374
2020	0.37012