Year	Percent
1960	3.28076
1961	3.3115
1962	3.34652
1963	3.40122
1964	3.47935
1965	3.55989
1966	3.6505
1967	3.70003
1968	3.64824
1969	3.47804
1970	3.2409
1971	2.98577
1972	2.77874
1973	2.65351
1974	2.63327
1975	2.68123
1976	2.74393
1977	2.77871
1978	2.78452
1979	2.74967
1980	2.68883
1981	2.62414
1982	2.57305
1983	2.53543
1984	2.51589
1985	2.50696
1986	2.49334
1987	2.47064
1988	2.44671
1989	2.42108
1990	2.62245
1991	2.13215
1992	2.34439
1993	2.27246
1994	1.9631
1995	1.80688
1996	1.91269
1997	1.88524
1998	1.60949
1999	1.07791
2000	1.38375
2001	1.26597
2002	1.22383
2003	1.16368
2004	1.15377
2005	1.16335
2006	1.22022
2007	1.42347
2008	1.60533
2009	1.68734
2010	2.82285
2011	2.68402
2012	1.4721
2013	1.5619
2014	1.6869
2015	1.74426
2016	1.73885
2017	1.67918