Year	Percent
1960	2.6307
1961	2.67615
1962	3.00176
1963	4.1165
1964	3.92217
1965	3.68265
1966	3.35915
1967	11.03005
1968	10.79216
1969	10.72062
1970	10.78037
1971	17.89437
1972	17.58011
1973	16.65602
1974	15.1084
1975	-187.1412
1976	5.77781
1977	4.46072
1978	3.91233
1979	4.55347
1980	48.93559
1981	26.09168
1982	4.72941
1983	5.78284
1984	6.03586
1985	5.73613
1986	5.34744
1987	5.13647
1988	5.06066
1989	5.16276
1990	5.39675
1991	5.60525
1992	5.69942
1993	5.69185
1994	5.56407
1995	5.35682
1996	5.14684
1997	4.94334
1998	4.25745
1999	3.05981
2000	2.86214
2001	2.66483
2002	2.47894
2003	2.33351
2004	2.24375
2005	2.19341
2006	2.14644
2007	2.10955
2008	2.28984
2009	3.31717
2010	3.34899
2011	3.39067
2012	3.42429
2013	3.43078
2014	3.41528
2015	3.37227
2016	3.32497
2017	3.27704