Year	%
1981	3.3
1986	5.2
1989	3.7
1990	3.8
1991	3.6
1992	4
1993	3.9
1994	4
1995	4
1996	3.8
1997	4.2
1998	4.3
1999	3.9
2000	3.9
2001	3.5
2002	3.5
2003	3.7
2004	4
2005	4.2
2006	4.1
2007	4.3
2008	4.3
2009	4
2010	4.4
2011	4.2
2012	4.2
2013	4.1
2014	4.2
2015	4.3
2016	4.2
2017	4.4
2018	4.3
2019	4.4
2020	4
2021	4.3
2022	4.5