Year	Percent
1960	4.0053
1961	3.98587
1962	2.50595
1963	1.95192
1964	1.95668
1965	1.93978
1966	1.9434
1967	1.94609
1968	2.51141
1969	2.71423
1970	2.73429
1971	2.73295
1972	2.72976
1973	2.72487
1974	2.71842
1975	3.44443
1976	3.72869
1977	3.72751
1978	3.72156
1979	3.73875
1980	3.7228
1981	3.72907
1982	9.70649
1983	19.59727
1984	19.28222
1985	18.51843
1986	17.5073
1987	16.50679
1988	13.97941
1989	10.67827
1990	8.18311
1991	5.77298
1992	3.3103
1993	1.04643
1994	-0.42209
1995	-1.17309
1996	-1.88236
1997	-2.51724
1998	-3.06858
1999	-3.53019
2000	-3.19325
2001	-2.14373
2002	-1.20222
2003	-0.31744
2004	0.55032
2005	1.41468
2006	1.80403
2007	1.71326
2008	1.61634
2009	1.50013
2010	1.38209
2011	1.24899
2012	1.11737
2013	0.98035
2014	0.84722
2015	0.70792
2016	0.61222
2017	0.54937