Year	Percent
1991	25.56671
1992	25.12942
1993	24.50012
1994	23.70679
1995	22.87444
1996	21.98437
1997	21.07161
1998	20.25701
1999	19.44603
2000	18.6708
2001	19.19592
2002	19.6323
2003	18.19592
2004	17.60554
2005	17.37805
2006	15.79108
2007	14.74489
2008	13.97101
2009	13.28457
2010	13.05422
2011	12.90796
2012	12.57882
2013	11.99881
2014	11.49089
2015	11.53419
2016	10.58418
2017	10.22169
2018	9.61849
2019	9.15711