Year	Percent
1991	56.111
1992	56.117
1993	55.966
1994	55.664
1995	55.311
1996	55.322
1997	55.498
1998	55.592
1999	55.684
2000	55.691
2001	55.694
2002	55.441
2003	55.714
2004	55.642
2005	57.521
2006	59.499
2007	61.491
2008	63.493
2009	65.564
2010	67.448
2011	69.54
2012	69.59
2013	69.629
2014	69.662
2015	69.657
2016	69.221
2017	68.812
2018	68.468
2019	68.146
2020	67.849
2021	67.574
2022	67.321