Year	% of total
1971	0
1972	0
1973	0
1974	0
1975	0
1976	0
1977	0
1978	0
1979	0
1980	0.2288527425739281
1981	0.18268826591651308
1982	0.2130126953125
1983	0.1821078989301161
1984	0.2408648877818702
1985	0.23667486425284276
1986	0.37661557626854714
1987	0.5504052124600317
1988	0.37655215421580673
1989	0.6342230810006668
1990	0.4460232942948937
1991	0.35845784910533113
1992	0.32715752230227657
1993	0.37261494825256236
1994	0.33978098454610584
1995	0.29754522707294473
1996	0.26179367547952304
1997	0.7110736269773077
1998	0.5217987152034261
1999	0.38816801311690124
2000	0.42581973803197964
2001	0.33316474773945626
2002	0.2535419704454939
2003	0.2697886437560022
2004	0.33855199586839496
2005	0.4855894861197873
2006	0.8311019646512121
2007	1.0331861575542616
2008	0.9969470910839773
2009	1.5393556121958698
2010	1.859881006498612
2011	2.0390613027674993
2012	1.981570924976508
2013	1.9612192767972876
2014	2.021005181136814
2015	2.4870306381175866