Year	Percent
1990	2.84
1992	2.53
1994	2.44
1996	3.86
1997	4.16
1998	3.85
1999	3.66
2000	3.82
2001	3.48
2002	3.48
2003	3.31
2004	3.4
2005	3.24
2006	3
2007	2.83
2008	2.65
2009	2.49
2010	4.55
2011	5.04
2012	5.01
2013	4.81
2014	4.39
2015	4.34
2016	4.35
2017	4.29