Year	%
1988	3.41
1989	5
1990	5.47
1991	5.02
1992	5.29
1993	4.61
1994	5.1
1995	4.79
1996	4.67
1997	3.74
1998	3.66
1999	3.04
2000	3.02
2001	3.23
2002	3.14
2003	2.99
2004	2.58
2005	2.4
2006	2.3
2007	2.26
2008	2.31
2009	2.39
2010	2.18
2011	2.3
2012	2.18
2013	2.19
2014	2.07
2015	2.13
2016	2.21
2017	2.02