Year	Percent
1971	7.2829
1972	10.61174
1973	7.74696
1974	5.81718
1975	3.69484
1976	5.86733
1977	4.20744
1978	6.50414
1979	4.55861
1980	3.946
1981	3.56336
1982	2.57369
1983	4.70954
1984	4.94063
1985	2.05862
1986	3.50222
1987	1.38206
1988	1.1904
1989	1.89003
1990	5.14356
1991	7.29542
1992	7.77649
1993	8.58607
1994	9.87913
1995	12.43381
1996	14.27581
1997	19.05384
1998	14.89695
1999	11.96983
2000	10.93436
2001	13.98075
2002	14.86362
2003	12.20024
2004	7.47975
2005	13.92404
2006	13.99519
2007	20.53278
2008	5.40391
2009	6.62973
2010	5.54523
2011	4.03333
2012	4.01142
2013	4.16428
2014	5.16503
2015	3.81421
2016	4.29843