Year	Percent
1971	13.88027
1972	9.9645
1973	7.47093
1974	2.83161
1975	14.758
1976	20.3148
1977	16.72614
1978	13.318
1979	12.88787
1980	15.27223
1981	15.62839
1982	14.08972
1983	7.6885
1984	8.21101
1985	13.63483
1986	15.67728
1987	17.51418
1988	6.25071
1989	5.12054
1990	1.39396
1991	1.42837
1992	1.76825
1993	1.24089
1994	1.65557
1995	1.86625
1996	1.64324
1997	0.64477
1998	0.84542
1999	0.75967
2000	3.46801
2001	3.47537
2002	-0.03297
2003	2.25265
2004	3.57263
2005	2.03357
2006	2.98265
2007	4.62632
2008	3.07611
2009	0.51789
2010	3.72935
2011	2.06915
2012	-0.50271
2013	4.86089
2014	0.55865
2015	0.68166
2016	3.17518
2017	3.41591