Year	Percent
1990	21.698
1991	21.411
1992	21.215
1993	21.061
1994	20.918
1995	20.641
1996	20.247
1997	19.858
1998	19.482
1999	19.128
2000	18.89
2001	18.537
2002	18.346
2003	18.244
2004	18.187
2005	18.137
2006	18.092
2007	18.053
2008	18.023
2009	18.044
2010	18.191
2011	18.255
2012	18.427
2013	18.663
2014	18.909
2015	19.135
2016	19.273
2017	19.301
2018	19.333
2019	19.365
2020	19.394
2021	19.421
2022	19.447
2023	19.471
2024	19.496
2025	19.522
2026	19.55
2027	19.578
2028	19.606
2029	19.634
2030	19.66