Year	Percent
1977	0.36336
1978	0.25973
1979	0.33107
1980	0.56517
1981	0.4878
1982	0.30232
1983	0.33888
1984	0.31086
1985	0.78662
1986	4.7246
1987	29.27533
1988	12.75733
1989	17.49246
1990	11.9542
1991	10.42471
1992	9.05767
1993	13.05331
1994	16.30881
1995	15.54086
1996	19.96305
1997	33.28043
1998	50.77683
1999	53.46366
2000	51.26856
2001	38.12372
2002	31.91966
2003	35.33175
2004	37.1274
2005	33.94418
2006	49.9539
2007	55.06054
2008	26.2878
2009	40.30725
2010	34.40853
2011	25.19033
2012	30.28127
2013	35.02308
2014	25.15971
2015	30.00557
2016	27.90427
2017	34.7425