Year	Percent
1991	15.66351
1992	15.41385
1993	15.19261
1994	14.95698
1995	14.6021
1996	14.2498
1997	13.36717
1998	12.42937
1999	11.63496
2000	10.88288
2001	10.0917
2002	9.39007
2003	9.2979
2004	9.30321
2005	9.28911
2006	9.28537
2007	9.251
2008	9.01955
2009	8.87752
2010	8.71115
2011	8.57602
2012	8.38281
2013	8.20028
2014	7.94861
2015	7.72806
2016	7.51012
2017	7.26746
2018	7.04227
2019	6.83383