Year	Percent
1991	68.04
1992	67.933
1993	68.874
1994	69.55
1995	68.691
1996	71.338
1997	70.824
1998	70.493
1999	70.793
2000	69.904
2001	70.016
2002	69.576
2003	69.743
2004	69.763
2005	69.824
2006	69.209
2007	68.852
2008	69.136
2009	69.016
2010	68.979
2011	68.936
2012	68.901
2013	68.851
2014	68.762
2015	68.377
2016	67.998
2017	67.858
2018	67.925
2019	67.925
2020	67.897
2021	67.855
2022	67.808