Year	Percent
1990	84.577
1991	84.628
1992	84.644
1993	84.642
1994	84.555
1995	84.478
1996	84.328
1997	84.151
1998	83.948
1999	83.717
2000	83.458
2001	83.214
2002	82.941
2003	82.643
2004	82.323
2005	81.99
2006	81.716
2007	81.434
2008	81.155
2009	80.902
2010	80.687
2011	80.645
2012	80.633
2013	80.618
2014	80.631
2015	80.633
2016	80.622
2017	80.782
2018	80.926
2019	81.042
2020	81.124
2021	81.2
2022	81.244
2023	81.265
2024	81.281
2025	81.306
2026	81.36
2027	81.421
2028	81.485
2029	81.545
2030	81.599