Year	% of total
1971	0.8674827488947172
1972	0.6106078855866707
1973	0.6030569483657812
1974	0.48204811438875206
1975	0.5111070923801961
1976	0.26223509606118023
1977	0.22866287946744893
1978	0.19031935050669915
1979	0.10246800845842279
1980	0.24270843749957766
1981	0.2215967066895244
1982	0.18568257076336137
1983	0.22043474878960106
1984	0.19868567205467347
1985	0.21075465322502243
1986	0.16837106067254176
1987	0.1673631279249152
1988	0.1675275475050914
1989	0.16487019289099963
1990	1.929344525029916
1991	1.818485397602027
1992	1.0280635587612572
1993	0.9218813955766831
1994	0.641655429844268
1995	0.6057653016091067
1996	0.6861480500154541
1997	0.716695016200367
1998	0.6708739882553659
1999	0.39274379028848017
2000	2.2515614370071853
2001	2.5773966326471407
2002	2.8239917962204477
2003	2.6435213909873054
2004	2.5155191720359396
2005	3.1119191223953053
2006	3.036416551799498
2007	3.3458635374667174
2008	3.365787666715573
2009	2.706384120795325
2010	2.62815761830476
2011	2.8630986844840405
2012	2.9414097563629644
2013	3.186328155352696
2014	2.933610222454187
2015	3.720611230773356