Year	Percent
1960	4.18526
1961	4.12831
1962	3.99922
1963	3.62065
1964	3.40206
1965	2.93026
1966	2.68328
1967	2.74793
1968	2.54364
1969	2.27378
1970	2.18898
1971	2.13149
1972	2.01182
1973	1.8326
1974	1.78381
1975	1.86354
1976	1.76593
1977	1.80576
1978	1.84889
1979	1.71125
1980	1.76445
1981	1.70992
1982	1.95434
1983	2.0812
1984	2.11719
1985	2.09738
1986	2.1092
1987	2.06258
1988	1.98677
1989	1.93461
1990	1.95879
1991	1.89544
1992	1.86169
1993	1.82175
1994	1.69668
1995	1.55409
1996	1.40375
1997	1.24624
1998	1.25629
1999	1.2417
2000	1.11808
2001	1.13737
2002	1.12085
2003	1.11588
2004	1.10797
2005	1.11067
2006	1.12583
2007	1.1889
2008	1.24862
2009	1.38104
2010	1.19715
2011	1.19608
2012	1.1211
2013	1.00486
2014	0.99581
2015	1.15591
2016	1.18587
2017	1.25396