Year	Percent
1991	3.73
1992	2.4
1993	2
1994	2.6
1995	3
1996	3.6
1997	2.6
1998	3.3
1999	4.4
2000	4.6
2001	4.4
2002	4.5
2003	4.7
2004	4
2005	3.8
2006	3.8
2007	2.9
2008	2.8
2009	2.79
2010	2.06
2011	2.18
2012	1.65
2013	1.4
2014	1.4
2015	1.57
2016	1.5
2017	1.6