Year	Percent
1979	4.10033
1980	4.08691
1981	7.2114
1982	7.06399
1983	5.32773
1984	5.48705
1985	3.73956
1986	1.69972
1987	9.85451
1988	7.27965
1989	6.34582
1990	8.27741
1991	13.48786
1992	13.48656
1993	13.80682
1994	13.58484
1995	13.27261
1996	13.35037
1997	11.81495
1998	7.77098
1999	5.00127
2000	7.44669
2001	6.9804
2002	5.39312
2003	5.72745
2004	5.43589
2005	3.35516
2006	9.88833
2007	6.48811
2008	6.20017
2009	5.26842
2010	9.00528
2011	7.71543
2012	7.72525
2013	7.40585
2014	1.62784
2015	4.20389
2016	2.74476
2017	2.86303