Year	%
1988	4.33
1989	5.63
1990	6.48
1991	5.84
1992	5.97
1993	6.17
1994	6.1
1995	5.59
1996	5.6
1997	4.71
1998	4.42
1999	4.31
2000	4.05
2001	4.27
2002	4.07
2003	4.13
2004	3.48
2005	3.3
2006	3.19
2007	3.06
2008	3.2
2009	3.22
2010	3.04
2011	3.14
2012	2.99
2013	3.01
2014	3.02
2015	3.18
2016	3.09
2017	3.39