Year	Percent
1991	83.703
1992	84.181
1993	86.194
1994	83.734
1995	84.068
1996	84.431
1997	84.035
1998	82.343
1999	82.569
2000	82.428
2001	82.924
2002	83.229
2003	82.479
2004	82.368
2005	83.042
2006	82.234
2007	82.156
2008	83.051
2009	80.866
2010	80.257
2011	80.137
2012	82.715
2013	81.922
2014	82.062
2015	81.578
2016	81.45
2017	81.349
2018	81.272
2019	81.194
2020	81.118
2021	81.043
2022	80.969