Year	Percent
1990	20.028
1991	19.99
1992	19.939
1993	19.879
1994	19.792
1995	19.712
1996	19.675
1997	19.618
1998	19.558
1999	19.493
2000	19.411
2001	19.355
2002	19.276
2003	19.228
2004	19.178
2005	19.13
2006	19.098
2007	19.082
2008	19.062
2009	19.04
2010	19.031
2011	19.02
2012	19.02
2013	19.013
2014	19.006
2015	19.003
2016	19.003
2017	18.983
2018	18.963
2019	18.944
2020	18.924
2021	18.904
2022	18.884
2023	18.864
2024	18.844
2025	18.824
2026	18.804
2027	18.784
2028	18.765
2029	18.745
2030	18.725