Year	Percent
1960	3.22116
1961	3.23215
1962	3.24336
1963	3.2465
1964	3.26434
1965	3.28426
1966	3.26868
1967	5.75618
1968	5.78736
1969	5.84503
1970	5.95361
1971	6.08044
1972	6.16357
1973	5.61509
1974	4.66518
1975	4.2327
1976	3.77244
1977	3.39086
1978	3.25806
1979	3.41182
1980	3.7775
1981	4.16418
1982	4.50536
1983	4.74812
1984	4.89568
1985	4.98844
1986	5.08686
1987	5.13487
1988	5.14514
1989	5.11908
1990	5.08034
1991	5.02581
1992	4.95337
1993	4.83898
1994	4.6847
1995	5.38742
1996	6.95448
1997	6.7288
1998	6.54121
1999	6.38355
2000	6.25566
2001	6.10662
2002	5.98542
2003	5.88926
2004	5.85686
2005	5.10036
2006	3.68929
2007	3.72875
2008	3.72368
2009	3.63064
2010	3.49879
2011	3.34961
2012	3.23226
2013	3.15598
2014	3.16348
2015	3.21628
2016	3.28549
2017	3.32201