Year	Percent
1960	1.81213
1961	1.87587
1962	1.93404
1963	1.98811
1964	2.04051
1965	2.09071
1966	2.13875
1967	2.18369
1968	2.22683
1969	2.26788
1970	2.30853
1971	2.34927
1972	2.39043
1973	2.43204
1974	2.47374
1975	2.51627
1976	2.5191
1977	2.51878
1978	2.58701
1979	2.74213
1980	2.92864
1981	3.11147
1982	3.19923
1983	3.12002
1984	2.84192
1985	2.42936
1986	2.09015
1987	1.79023
1988	1.31772
1989	0.62964
1990	-0.15619
1991	-1.09995
1992	-1.86759
1993	-1.96385
1994	-1.08358
1995	0.51015
1996	2.38179
1997	3.90913
1998	4.80063
1999	4.89377
2000	4.49916
2001	4.00469
2002	3.69926
2003	3.5877
2004	3.74179
2005	4.04196
2006	4.33529
2007	4.48732
2008	4.48571
2009	4.30546
2010	4.01845
2011	3.72108
2012	3.47427
2013	3.26667
2014	3.11346
2015	2.99995
2016	2.89155
2017	2.78159