Year	Percent
1991	83.916
1992	83.58
1993	84.05
1994	84.01
1995	84.32
1996	84.267
1997	84.078
1998	84.515
1999	84.08
2000	83.293
2001	83.779
2002	86.055
2003	85.346
2004	83.79
2005	83.763
2006	82.838
2007	82.807
2008	83.022
2009	82.816
2010	82.127
2011	81.277
2012	80.994
2013	80.564
2014	80.666
2015	81.355
2016	81.495
2017	81.521
2018	81.515
2019	81.503
2020	81.481
2021	81.46
2022	81.439