Year	Percent
1971	34.06437
1972	43.77473
1973	76.0039
1974	111.20012
1975	91.73094
1976	82.40341
1977	52.02249
1978	38.35139
1979	43.12562
1980	31.84365
1981	20.09185
1982	8.45645
1983	5.34714
1984	2.57613
1985	4.15045
1986	5.40649
1987	3.03448
1988	1.94336
1989	1.56633
1990	0.6384
1991	1.16533
1992	2.88657
1993	5.14473
1994	5.82899
1995	7.89436
1996	8.35644
1997	5.83148
1998	5.77588
1999	9.80891
2000	6.57247
2001	8.52608
2002	14.74102
2003	13.12323
2004	22.59637
2005	16.73692
2006	38.03318
2007	48.57802
2008	29.97323
2009	32.88059
2010	30.5564
2011	32.95348
2012	22.00035
2013	18.79514
2014	21.5902
2015	19.04328
2016	13.14204