Year	%
1988	5.75
1989	6.91
1990	7.8
1991	7.02
1992	8.15
1993	8.85
1994	9.69
1995	7.35
1996	7.1
1997	6.42
1998	6.03
1999	6.54
2000	5.84
2001	6.17
2002	5.74
2003	5.55
2004	4.96
2005	4.7
2006	4.34
2007	4.5
2008	4.53
2009	4.32
2010	4.3
2011	4.56
2012	3.93
2013	4.06
2014	4.11
2015	4.3
2016	4.1
2017	4.17