Year	Percent
1999	3.69
2000	3.78
2001	3.87
2002	4.21
2003	4.36
2004	4.49
2005	4.6
2006	4.71
2007	4.21
2008	3.54
2009	3.53
2010	3.45
2011	3.35
2012	2.67
2013	2.78
2014	2.76
2015	2.44
2016	2.51
2017	3.22