Year	Percent
1991	68.839
1992	68.745
1993	68.632
1994	68.561
1995	68.48
1996	68.46
1997	68.404
1998	68.343
1999	68.274
2000	68.203
2001	68.144
2002	68.106
2003	68.093
2004	68.094
2005	68.1
2006	68.111
2007	68.119
2008	68.128
2009	68.128
2010	68.141
2011	68.171
2012	68.202
2013	68.233
2014	68.26
2015	68.27
2016	68.282
2017	68.29
2018	68.294
2019	68.294
2020	68.293
2021	68.287
2022	68.284