Year	Percent
1981	4.38259
1982	7.4664
1983	6.64043
1984	10.04206
1985	6.31259
1986	6.68496
1987	0.40387
1988	14.69955
1989	5.5056
1990	5.70885
1991	8.76415
1992	9.29676
1993	8.18646
1994	12.85199
1995	8.04782
1996	8.05613
1997	12.4854
1998	10.50963
1999	7.43531
2000	2.28621
2001	5.26631
2002	4.88122
2003	3.08507
2004	3.79093
2005	5.85793
2006	5.41119
2007	3.11066
2008	5.65307
2009	4.85125
2010	5.98551
2011	8.60716
2012	9.18074
2013	5.86439
2014	7.28055
2015	3.64747
2016	4.23731
2017	7.54893