Year	Percent
1960	4.20716
1961	3.74375
1962	3.39679
1963	3.60138
1964	3.6724
1965	3.74009
1966	3.91882
1967	3.80005
1968	3.48608
1969	3.10587
1970	3.16675
1971	3.35871
1972	3.6161
1973	3.58706
1974	3.24977
1975	3.64423
1976	4.0962
1977	3.7685
1978	3.60031
1979	3.52933
1980	3.39915
1981	2.12164
1982	0.52772
1983	0.9529
1984	0.83652
1985	0.81296
1986	1.57109
1987	1.52715
1988	0.59408
1989	0.37888
1990	0.41063
1991	0.31523
1992	-0.09529
1993	-0.18688
1994	-0.06227
1995	0.07289
1996	-0.00923
1997	-0.08313
1998	-0.16678
1999	0.12464
2000	0.34732
2001	0.20871
2002	0.27543
2003	0.50172
2004	0.50556
2005	0.61074
2006	0.75483
2007	0.99292
2008	0.592
2009	1.33202
2010	0.86426
2011	0.6341
2012	0.63459
2013	0.55661
2014	0.5194
2015	0.49257
2016	0.5166
2017	0.54979