Year	Percent
1970	5.39908
1971	5.6417
1972	5.08581
1973	4.70463
1974	4.29417
1975	4.64926
1976	5.04436
1977	5.67716
1978	5.19524
1979	4.65202
1980	4.63686
1981	4.74136
1982	4.65119
1983	4.07147
1984	4.69882
1985	5.65661
1986	5.44251
1987	4.87061
1988	4.54787
1989	4.4929
1990	4.63214
1991	4.44836
1992	4.47137
1993	4.09176
1994	3.79144
1995	4.1788
1996	4.25331
1997	4.45004
1998	5.21105
1999	5.20735
2000	4.51889
2001	4.82625
2002	4.92499
2003	4.86965
2004	4.41681
2005	4.28813
2006	3.94503
2007	3.62178
2008	3.87779
2009	3.91761
2010	3.42985
2011	3.23735
2012	3.17185
2013	3.08937
2014	3.11421
2015	3.16129
2016	3.32828
2017	3.32116