Year	Percent
1997	75
1998	83.4
1999	88.3
2000	90.4
2001	85.3
2002	76.1
2003	68.6
2004	69.2
2005	74.4
2006	40.6
2007	31.5
2008	32.9
2009	31.5
2010	29
2011	25.6
2012	24.6
2013	19.7
2014	18.4
2015	16.3
2016	16.5