Year	Percent
1990	84.227
1991	83.974
1992	83.536
1993	82.871
1994	82.712
1995	83.013
1996	82.775
1997	83.104
1998	83.41
1999	83.446
2000	83.672
2001	83.785
2002	83.894
2003	83.906
2004	83.897
2005	83.743
2006	83.753
2007	83.561
2008	83.385
2009	83.223
2010	82.984
2011	82.589
2012	82.297
2013	82.125
2014	81.781
2015	81.522
2016	81.5
2017	81.454
2018	81.406
2019	81.357
2020	81.305
2021	81.252
2022	81.198
2023	81.143
2024	81.09
2025	81.039
2026	80.99
2027	80.942
2028	80.896
2029	80.851
2030	80.804