Year	Percent
1990	86.914
1991	86.95
1992	86.966
1993	86.829
1994	87.001
1995	86.718
1996	86.53
1997	86.689
1998	86.592
1999	86.316
2000	86.32
2001	86.073
2002	85.822
2003	85.567
2004	85.309
2005	85.049
2006	84.784
2007	84.517
2008	84.248
2009	83.976
2010	83.701
2011	83.418
2012	83.132
2013	82.91
2014	82.751
2015	82.73
2016	82.727
2017	82.689
2018	82.652
2019	82.615
2020	82.578
2021	82.539
2022	82.5
2023	82.46
2024	82.42
2025	82.379
2026	82.335
2027	82.29
2028	82.244
2029	82.197
2030	82.148