Year	% of total
1971	0.07795813914384161
1972	0.0756109819274842
1973	0.06997961465569309
1974	0.06919510241805822
1975	0.12064142127469457
1976	0.2240960570538591
1977	0.20928520597033765
1978	0.21439541955654123
1979	0.32668825632805654
1980	0.6455387817745761
1981	0.8745202048453301
1982	0.9954915462544295
1983	1.1072397452793732
1984	1.114022599005372
1985	1.0804343542382666
1986	0.9867972895943152
1987	0.8830201242207948
1988	0.8833750147217474
1989	0.8860354040252663
1990	0.858064782482407
1991	0.8248298104143544
1992	0.814791746574323
1993	0.792332194471492
1994	0.9067080402474349
1995	0.9146682441114924
1996	0.9630347184003587
1997	1.0092961693527647
1998	1.1008050695061988
1999	1.2699764332426127
2000	1.5139859415117842
2001	1.549291886712751
2002	1.5544945616434416
2003	1.5919797868368242
2004	1.6835251975352232
2005	1.7351301712554952
2006	1.9415198821735973
2007	2.062525079698998
2008	2.309728788207439
2009	2.602367224577287
2010	2.616451101453015
2011	2.82045266860815
2012	3.111707766300231
2013	3.307081179720306
2014	3.5984720368613985
2015	3.7946666293388374