Year	Percent
1990	58.976
1991	57.722
1992	56.324
1993	55.487
1994	54.781
1995	54.755
1996	54.645
1997	54.778
1998	54.988
1999	56.146
2000	56.189
2001	56.533
2002	56.862
2003	56.529
2004	56.313
2005	56.622
2006	57.085
2007	57.471
2008	57.439
2009	57.021
2010	56.025
2011	55.811
2012	55.944
2013	55.5
2014	55.506
2015	55.521
2016	54.954
2017	54.807
2018	54.682
2019	54.561
2020	54.429
2021	54.303
2022	54.181
2023	54.067
2024	53.963
2025	53.868
2026	53.818
2027	53.784
2028	53.766
2029	53.765
2030	53.779