Year	Percent
1990	57.72
1991	57.704
1992	57.665
1993	57.552
1994	57.494
1995	57.419
1996	57.388
1997	57.325
1998	57.229
1999	57.111
2000	56.989
2001	56.923
2002	56.848
2003	56.77
2004	56.688
2005	56.593
2006	56.567
2007	56.524
2008	56.471
2009	56.411
2010	56.364
2011	56.364
2012	56.357
2013	56.347
2014	56.323
2015	56.28
2016	56.235
2017	56.185
2018	56.134
2019	56.084
2020	56.034
2021	55.984
2022	55.933
2023	55.883
2024	55.833
2025	55.782
2026	55.732
2027	55.682
2028	55.632
2029	55.581
2030	55.531