Year	Percent
1980	0.29
1981	0.303
1982	0.261
1983	0.247
1984	0.251
1985	0.247
1986	0.252
1987	0.259
1988	0.265
1989	0.283
1990	0.282
1991	0.297
1992	0.296
1993	0.31
1994	0.316
1995	0.332
1996	0.342
1997	0.353
1998	0.359
1999	0.345
2000	0.347
2001	0.35
2002	0.35
2003	0.35
2004	0.357
2005	0.36
2006	0.364
2007	0.362
2008	0.364
2009	0.36
2010	0.362
2011	0.369
2012	0.376
2013	0.379
2014	0.373
2015	0.369
2016	0.363
2017	0.355
2018	0.356
2019	0.357
2020	0.356
2021	0.354
2022	0.352
2023	0.35
2024	0.348