Year	Percent
1991	21.75859
1992	21.57577
1993	21.39558
1994	21.13681
1995	20.86479
1996	20.5263
1997	20.09576
1998	19.68366
1999	19.2834
2000	18.96086
2001	19.01801
2002	18.55523
2003	17.85767
2004	17.30579
2005	17.36013
2006	16.31273
2007	15.57222
2008	14.78649
2009	14.22327
2010	13.36856
2011	12.55102
2012	11.90125
2013	11.15266
2014	10.4141
2015	9.83023
2016	9.23625
2017	8.95451
2018	8.59429
2019	8.32235