Year	Percent
1990	81.807
1991	81.954
1992	82.121
1993	82.316
1994	82.305
1995	82.266
1996	82.228
1997	82.103
1998	81.902
1999	81.82
2000	81.723
2001	81.689
2002	81.679
2003	81.741
2004	81.783
2005	81.804
2006	81.828
2007	81.807
2008	81.828
2009	81.938
2010	81.968
2011	81.982
2012	82.019
2013	82.051
2014	82.023
2015	81.916
2016	81.785
2017	81.598
2018	81.392
2019	81.218
2020	81.102
2021	81.043
2022	81.037
2023	81.053
2024	81.045
2025	80.988
2026	80.895
2027	80.763
2028	80.616
2029	80.494
2030	80.419