Year	Percent
1998	18.31
1999	19.25
2000	16.82
2001	18.03
2002	18.33
2003	17.52
2004	16.41
2005	17.78
2006	17.67
2007	17.38
2008	17.57
2009	17.39
2010	16.64
2011	16.91
2012	16.14
2013	15.12
2014	15.74
2016	12.35
2017	9.64