Year	Percent
1991	0.46308
1992	0.4514
1993	0.4424
1994	0.43223
1995	0.42308
1996	0.4152
1997	0.40507
1998	0.39843
1999	0.39838
2000	0.3985
2001	0.39834
2002	0.39825
2003	0.39823
2004	0.39822
2005	0.39848
2006	0.39824
2007	0.39843
2008	0.39833
2009	0.39835
2010	0.39842
2011	0.39848
2012	0.39834
2013	0.39851
2014	0.39837
2015	0.39847
2016	0.39834
2017	0.39847
2018	0.3988
2019	0.39937