Year	Percent
1970	4.03008
1971	3.74169
1972	3.27366
1973	3.00699
1974	3.20784
1975	3.33541
1976	3.00624
1977	2.95533
1978	3.23964
1979	3.23904
1980	3.34258
1981	3.33376
1982	3.24331
1983	3.33594
1984	3.14768
1985	4.97243
1986	3.22373
1987	3.15558
1988	3.59622
1989	2.78616
1990	2.56354
1991	2.16147
1992	2.17965
1993	1.90657
1994	1.82413
1995	1.32473
1996	1.25906
1997	1.47668
1998	1.27216
1999	1.43361
2000	1.51762
2001	1.57495
2002	1.5985
2003	1.64893
2004	1.47877
2005	1.41836
2006	1.22899
2007	1.2773
2008	1.18901
2009	1.13722
2010	1.03836
2011	1.052
2012	1.03972
2013	0.95241
2014	0.87447
2015	0.93836
2016	1.0364
2017	1.05493