Year	Percent
1960	3.31631
1961	3.40504
1962	3.44119
1963	3.38693
1964	3.22791
1965	3.00424
1966	2.76834
1967	2.55821
1968	2.37391
1969	2.22683
1970	2.10885
1971	1.99742
1972	1.88828
1973	1.80008
1974	1.73556
1975	1.68951
1976	1.65324
1977	1.62334
1978	1.60387
1979	1.59376
1980	1.59115
1981	1.59006
1982	1.59125
1983	1.60167
1984	1.62205
1985	1.64658
1986	1.66872
1987	1.68035
1988	1.67639
1989	1.65323
1990	0.44952
1991	1.55235
1992	1.51508
1993	1.51915
1994	1.35173
1995	1.15169
1996	1.00985
1997	0.96467
1998	0.94914
1999	0.8776
2000	0.82152
2001	0.77477
2002	0.74617
2003	0.75765
2004	0.87543
2005	1.02227
2006	1.09859
2007	1.13386
2008	2.09985
2009	2.07615
2010	1.18979
2011	1.303
2012	1.32876
2013	1.29345
2014	1.24821
2015	1.19121
2016	1.11786
2017	1.06643