Year	% of total
1971	2.758733792612449
1972	1.6226076859693688
1973	3.1678467816820657
1974	1.2623301783330731
1975	1.4089566004285787
1976	1.2241360843702154
1977	0.7050257915130999
1978	0.8749899900622403
1979	0.7269614268644664
1980	0.5941565765918561
1981	0.45866099532246696
1982	0.5207960083538086
1983	0.6088502971888251
1984	0.8256969881325835
1985	1.337218996907868
1986	1.8123829852904811
1987	3.096541045472002
1988	2.9767986287705943
1989	2.848460739552067
1990	2.607376979390555
1991	2.9673298420546668
1992	2.4857283423912326
1993	2.622564912242036
1994	2.5518122576974718
1995	2.497808266910822
1996	2.2475672452932614
1997	2.1902432903338864
1998	1.8646283937650654
1999	1.612119382226947
2000	2.5108243216815604
2001	3.076457823913976
2002	3.066232348500804
2003	2.598479716017252
2004	2.6797360000447523
2005	2.7954468675151447
2006	2.185070207474811
2007	2.153329021945795
2008	2.0151769464950307
2009	1.8838172546018317
2010	2.0910192856965457
2011	2.4989751222825785
2012	2.4744448503507983
2013	2.6127432174426937
2014	2.2068379923660504
2015	2.412971871922621