Year	Percent
1991	38.021
1992	37.918
1993	37.65
1994	37.527
1995	37.258
1996	37.19
1997	33.513
1998	33.589
1999	33.722
2000	33.693
2001	33.67
2002	33.546
2003	31.872
2004	31.766
2005	31.651
2006	31.336
2007	31.467
2008	31.636
2009	31.841
2010	31.433
2011	31.35
2012	31.495
2013	31.462
2014	31.462
2015	31.468
2016	31.509
2017	31.512
2018	31.505
2019	31.497
2020	31.49
2021	31.483
2022	31.476