Year	% of total
1971	1.1723344621406264
1972	2.274620517870834
1973	2.3872801207084193
1974	2.3512320635770485
1975	2.727442272084822
1976	2.4737858877942878
1977	2.2055993309081865
1978	2.00025331378573
1979	1.3676910567849025
1980	1.3949449665173392
1981	1.4484735898509369
1982	1.2282495111961294
1983	1.286662388020157
1984	1.053090684663597
1985	0.8929072492934891
1986	1.5010435419815948
1987	1.8020756706489158
1988	1.6393377576159627
1989	1.1728021140373253
1990	1.2254836491526624
1991	0.9871795677959473
1992	0.8411031234993512
1993	1.1840240780232139
1994	1.2782072515177043
1995	2.443302644363308
1996	2.288535538082569
1997	2.3181311431158576
1998	2.547417709914407
1999	2.301063987455161
2000	2.7090774587927706
2001	3.33150518319459
2002	3.0964775126847286
2003	2.990521151584387
2004	2.9520247449579196
2005	2.8409484028050493
2006	2.687755799394858
2007	2.4586725469054374
2008	2.144577514719104
2009	1.9291133568569683
2010	1.7730451007966603
2011	1.8613215992082706
2012	1.811044648448929
2013	1.7785108860612773
2014	2.2292809528889004
2015	2.341905314659116