Year	Percent
1971	23.88641
1972	27.57697
1973	3.0668
1974	20.08027
1975	2.13845
1976	14.93074
1977	9.53629
1978	4.8802
1979	5.54529
1980	4.14194
1981	4.57106
1982	7.98683
1983	14.74081
1984	24.53203
1985	17.13267
1986	7.69398
1987	16.51967
1988	17.0921
1989	29.14276
1990	25.68445
1991	20.06691
1992	13.12024
1993	6.2521
1994	10.23901
1995	17.43949
1996	17.80999
1997	14.53123
1998	11.97016
1999	8.8574
2000	10.3515
2001	11.44951
2002	17.43775
2003	12.4554
2004	13.7148
2005	14.1922
2006	35.97337
2007	52.16132
2008	75.18311
2009	32.90173
2010	29.31117
2011	40.53801
2012	48.94244
2013	40.44559
2014	44.91101
2015	22.81485
2016	0.49452