Year	Percent
1997	30.7
1998	30.7
1999	32.1
2000	32.2
2001	30.5
2002	27.81
2003	29.59
2004	30.8
2005	29.7
2006	35.3
2008	29.25
2009	26.14
2010	24.95
2011	25.52
2012	26.06
2013	26.3
2016	25.2