Year	Percent
1991	38.509
1992	37.68
1993	37.286
1994	36.591
1995	36.01
1996	35.471
1997	35.443
1998	35.473
1999	35.367
2000	35.44
2001	35.449
2002	35.367
2003	35.357
2004	35.293
2005	35.239
2006	35.149
2007	34.988
2008	34.789
2009	34.525
2010	34.293
2011	33.636
2012	33.055
2013	32.565
2014	31.932
2015	31.234
2016	30.609
2017	30.535
2018	30.472
2019	30.395
2020	30.313
2021	30.237
2022	30.159