Year	Percent
1991	80.003
1992	80.39
1993	80.555
1994	80.66
1995	80.651
1996	81.701
1997	82.121
1998	82.166
1999	81.536
2000	81.707
2001	81.894
2002	81.865
2003	82.423
2004	82.251
2005	82.116
2006	82.141
2007	82.063
2008	82.102
2009	81.953
2010	81.904
2011	82.013
2012	81.861
2013	81.691
2014	81.5
2015	81.691
2016	81.627
2017	81.703
2018	81.643
2019	81.583
2020	81.515
2021	81.444
2022	81.38