Year	Percent
1961	4.18906
1962	2.92397
1963	2.13301
1964	5.68451
1965	2.0771
1966	2.60567
1967	2.62112
1968	1.44868
1969	2.60517
1970	4.44558
1971	-2.77754
1972	3.86452
1973	5.34581
1974	14.77894
1975	6.3848
1976	8.53219
1977	12.19948
1978	5.0614
1979	11.48799
1980	13.21167
1981	7.16449
1982	4.43213
1983	6.96427
1984	3.37255
1985	5.24847
1986	3.89269
1987	2.83033
1988	6.48206
1989	7.07494
1990	21.20056
1991	26.02834
1992	9.10221
1993	13.60833
1994	28.88674
1995	24.87907
1996	22.92478
1997	22.27969
1998	11.62866
1999	11.56025
2000	30.81976
2001	8.08435
2002	5.13194
2003	5.75974
2004	6.45198
2005	7.27916
2006	5.34866
2007	6.62551
2008	7.79051
2009	7.65373
2010	4.67604
2011	7.80721
2012	3.57979
2013	1.37403
2014	6.84936
2015	6.93277
2016	3.46655
2017	4.21112