Year	Percent
1977	8.57941
1978	10.7518
1979	17.93647
1980	26.56957
1981	10.8639
1982	8.86524
1983	8.4367
1984	7.46367
1985	8.19952
1986	8.02256
1987	12.915
1988	10.88646
1989	11.04756
1990	10.121
1991	8.56428
1992	5.3554
1993	9.22022
1994	6.55543
1995	5.4032
1996	7.00204
1997	5.12077
1998	6.9649
1999	5.28307
2000	2.08598
2001	7.09983
2002	5.85383
2003	5.71479
2004	6.09058
2005	4.25896
2006	10.78479
2007	8.30832
2008	5.68669
2009	-0.6542
2010	1.12642
2011	3.16146
2012	2.46552
2013	2.75088
2014	1.48064
2015	1.04316
2016	2.1849
2017	1.91274