Year	Percent
1971	2.43707
1972	5.92581
1973	4.2323
1974	10.11073
1975	18.68526
1976	16.42315
1977	11.74708
1978	10.01006
1979	9.37649
1980	5.93305
1981	2.55486
1982	0.11384
1983	-2.00341
1984	0.9213
1985	0.79885
1986	2.1638
1987	3.39606
1988	7.52776
1989	7.13131
1990	5.2566
1991	3.43103
1992	3.61645
1993	3.44244
1994	4.66759
1995	5.60371
1996	3.09824
1997	4.46341
1998	4.44457
1999	4.10097
2000	6.08346
2001	-0.14449
2002	2.21793
2003	1.87152
2004	-0.22893
2005	3.1242
2006	1.45839
2007	3.62442
2008	2.67627
2009	-3.19486
2010	3.03535
2011	0.89443
2012	1.79334
2013	3.15258
2014	5.97687
2015	7.03661
2016	2.84961
2017	4.14991