Year	% of total
1960	0
1961	0
1962	0
1963	0
1964	0
1965	0
1966	0
1967	0
1968	0
1969	0
1970	0.05721232925695488
1971	0.316578369298359
1972	1.2206892636121047
1973	1.4138470670767904
1974	0.6479711068621202
1975	0.6953900019451469
1976	11.726323639075318
1977	19.032568366084927
1978	16.558675305975523
1979	7.1551489901277066
1980	7.541157727031333
1981	9.210189997443981
1982	19.663596315578694
1983	14.958668327482732
1984	17.004992893327017
1985	20.19189150194777
1986	16.548852183650617
1987	16.627176264551355
1988	15.242556038808965
1989	20.419031826009313
1990	17.69719510305284
1991	21.08661701105238
1992	22.78835045905028
1993	20.42596644784829
1994	15.709735732116725
1995	13.321501857911375
1996	18.139445617305952
1997	25.30113988520305
1998	20.288737636924388
1999	25.549356109686123
2000	24.389125283461155
2001	30.961285757606387
2002	25.20859484604593
2003	24.00617995438605
2004	16.49383408071749
2005	21.91630981195308
2006	22.593000321086187
2007	27.0655726464471
2008	24.291350254270142
2009	20.55094009619589
2010	22.082665241403884
2011	18.964548254389317
2012	20.01852521236219
2013	20.081815660534343
2014	16.159062176761292
2015	15.534441805225654