Year	Percent
1961	2.688
1962	5.89709
1963	3.56993
1964	1.19472
1965	12.88519
1966	15.21881
1967	-5.66767
1968	11.06583
1969	6.56383
1970	7.04833
1971	3.17218
1972	12.50268
1973	-3.39731
1974	20.82567
1975	27.52275
1976	0.54404
1977	-3.56482
1978	9.37121
1979	9.97836
1980	7.60955
1981	7.93736
1982	9.34741
1983	12.28869
1984	6.37795
1985	11.42183
1986	14.39257
1987	12.6968
1988	11.81531
1989	11.25837
1990	10.71589
1991	12.54464
1992	18.48909
1993	10.77491
1994	4.81599
1995	6.30086
1996	7.82304
1997	7.27909
1998	4.10785
1999	8.88705
2000	4.47243
2001	11.0174
2002	3.93462
2003	3.0703
2004	4.16643
2005	6.11939
2006	7.36004
2007	7.60329
2008	5.61985
2009	15.90833
2010	15.14693
2011	10.81117
2012	6.63496
2013	6.57724
2014	9.3522
2015	4.94281
2016	5.07174
2017	7.58551