Year	Percent
1960	10.45246
1961	11.17693
1962	10.67969
1963	10.28867
1964	9.7234
1965	9.22919
1966	8.75087
1967	8.28542
1968	7.88405
1969	7.56789
1970	7.3286
1971	7.15866
1972	6.92608
1973	6.54839
1974	6.00416
1975	5.3435
1976	4.71696
1977	4.24884
1978	3.97075
1979	4.12168
1980	4.40521
1981	4.69169
1982	4.93647
1983	5.04026
1984	4.99647
1985	4.87654
1986	4.38174
1987	3.9271
1988	3.84548
1989	3.75131
1990	3.68735
1991	3.69631
1992	3.62036
1993	3.24843
1994	2.5245
1995	1.6115
1996	0.54198
1997	-0.31316
1998	-0.56046
1999	0.07379
2000	1.27931
2001	2.57187
2002	3.49205
2003	3.89996
2004	3.59759
2005	2.86778
2006	2.12734
2007	1.51048
2008	1.07353
2009	0.61041
2010	-0.11992
2011	-0.93494
2012	-1.69647
2013	-2.11923
2014	-2.06373
2015	-1.64767
2016	-1.0531
2017	-0.52042