Year	Percent
1970	4.49643
1971	5.3885
1972	8.03253
1973	7.5154
1974	4.94172
1975	5.95462
1976	4.45356
1977	8.45697
1978	9.09239
1979	19.14278
1980	27.19666
1981	23.27762
1982	29.55332
1983	26.87214
1984	25.19268
1985	25.05838
1986	45.36737
1987	37.83323
1988	43.71191
1989	24.61541
1990	23.25361
1991	17.90392
1992	19.45971
1993	22.26653
1994	19.11086
1995	22.86428
1996	18.39895
1997	18.16428
1998	30.4519
1999	23.59515
2000	16.88664
2001	25.4546
2002	25.60826
2003	29.61133
2004	14.63352
2005	8.70922
2006	7.455
2007	10.55928
2008	10.42187
2009	18.82723
2010	22.86957
2011	22.11406
2012	23.7243
2013	24.82639
2014	30.11213
2015	60.37041
2016	59.54766