Year	% of total
1971	0
1972	0
1973	0
1974	0
1975	0
1976	0
1977	0
1978	0.0009814894915635482
1979	0.19011320768216045
1980	0.5784085056538877
1981	0.8387791508867747
1982	1.0020353218796643
1983	1.205354445078725
1984	1.2174654279791124
1985	1.2347547607667686
1986	1.067140793814423
1987	0.9328535643797486
1988	0.941747202599521
1989	0.9411593792549902
1990	0.9270621772458965
1991	0.8236540980669855
1992	0.7460221722185092
1993	0.670979291282199
1994	0.7666235296099778
1995	0.9361648224409134
1996	0.8410134216353946
1997	0.9161768784297706
1998	0.9999569366407698
1999	1.1044327226501855
2000	1.1868415973685447
2001	1.0988635275279075
2002	1.0090284858170506
2003	0.8980545741623334
2004	0.8363523191339209
2005	0.8599705481541002
2006	0.8865471203013314
2007	0.9136622476689356
2008	1.2835009298051852
2009	1.6733132856817305
2010	1.9458982378220575
2011	2.339088922647185
2012	2.780962568841149
2013	3.59681628965569
2014	4.043378314083713
2015	4.769249691167521