Year	% of total
1971	2.561147475242135
1972	1.554488003953085
1973	2.63069586090517
1974	1.2144366093965324
1975	1.2903117764007705
1976	1.0393116032693088
1977	0.6801273564255745
1978	0.7784866917046336
1979	0.6384775031721732
1980	0.5731764905036525
1981	0.4493224850330779
1982	0.46539310849911086
1983	0.6084016320374857
1984	0.8227082271640561
1985	1.266949573462745
1986	1.6581810082540929
1987	2.7912610227893064
1988	2.5960799338148832
1989	2.4051046595568155
1990	4.692219500382227
1991	4.820181062995825
1992	3.5178094460575906
1993	3.870931449074059
1994	3.9672718948648016
1995	3.1248762979246174
1996	3.017233476241262
1997	3.0065494917379056
1998	2.7717063023686386
1999	2.322029725742329
2000	3.06511478285674
2001	3.5232734864258797
2002	3.4708953597921206
2003	2.944008379351565
2004	2.974749263565128
2005	3.2718171118226467
2006	2.7608272018630875
2007	2.865697623873125
2008	2.843307000198164
2009	2.453700710253927
2010	2.5894326495496585
2011	2.943951142811465
2012	2.9208668135173785
2013	3.170685046814144
2014	2.996711781028626
2015	3.4499155083680377