Year	Percent
1990	60.018
1991	60.022
1992	59.952
1993	59.826
1994	59.667
1995	59.471
1996	59.333
1997	59.171
1998	58.978
1999	58.769
2000	58.593
2001	58.469
2002	58.372
2003	58.299
2004	58.253
2005	58.067
2006	58.069
2007	58.114
2008	58.186
2009	58.131
2010	58.139
2011	58.128
2012	58.074
2013	58.076
2014	58.06
2015	57.552
2016	57.999
2017	58.058
2018	58.121
2019	58.174
2020	58.207
2021	58.224
2022	58.219
2023	58.196
2024	58.162
2025	58.119
2026	58.069
2027	58.007
2028	57.933
2029	57.848
2030	57.754