Year	Percent
1997	4.1669
1998	4.9322
1999	6.1878
2000	7.0521
2001	6.5602
2002	7.5546
2003	6.6263
2004	7.3401
2005	6.6928
2006	7.2489
2007	6.2001
2008	5.7926
2009	6.7711
2010	6.7034
2011	6.5963
2012	6.487
2013	6.9062
2014	6.5659
2015	6.9053
2016	6.0196
2017	4.9401