Year	Percent
1990	0.29433
1991	0.28624
1992	0.2252
1993	0.21904
1994	0.22425
1995	0.24307
1996	0.23649
1997	0.27641
1998	0.2691
1999	0.30374
2000	0.25422
2001	0.37312
2002	0.36359
2003	0.35449
2004	0.34457
2005	0.33814
2006	0.33165
2007	0.32329
2008	0.31513
2009	0.30712
2010	0.29914
2011	0.29111
2012	0.29589
2013	0.30162
2014	0.29054
2015	0.34562
2016	0.33292
2017	0.34442
2018	0.34379
2019	0.33099
2020	0.32492