Year	Percent
1991	23.23535
1992	23.38408
1993	23.39144
1994	22.96457
1995	22.31044
1996	21.69742
1997	20.66016
1998	19.557
1999	19.98893
2000	19.24108
2001	17.57325
2002	18.63479
2003	18.71284
2004	16.28423
2005	14.27109
2006	13.8325
2007	11.32539
2008	8.06462
2009	8.98395
2010	8.8305
2011	8.48619
2012	8.79666
2013	8.42277
2014	9.16598
2015	9.06897
2016	7.97554
2017	7.78401
2018	7.18262
2019	6.42059