Year	Percent
1993	20.53
1994	16.74
1995	17.93
1996	17.46
1997	16.7
1998	15.82
1999	15.54
2000	14.14
2001	13.66
2002	14.32
2003	11.93
2004	16.14
2005	16.81
2006	17.35
2007	13.69
2008	15.23
2009	14.94
2010	16.24
2011	17.34
2012	18.17
2013	20.42
2014	20.72
2015	20.29
2016	18.99
2017	19.22