Year	% of total
1971	1.6339869281045754
1972	1.4184397163120568
1973	1.1799410029498525
1974	1.4634146341463417
1975	1.5873015873015872
1976	1.5655577299412915
1977	1.2975778546712802
1978	1.4059753954305798
1979	1.5334063526834611
1980	1.791044776119403
1981	1.650485436893204
1982	1.7964071856287425
1983	9.90888382687927
1984	31.47751605995717
1985	31.2015503875969
1986	23.30259849119866
1987	19.718309859154928
1988	22.03125
1989	30.21167415009622
1990	33.69938229238161
1991	37.88984737889847
1992	35.26540573520439
1993	29.164265129683
1994	26.517754868270334
1995	23.504043126684635
1996	21.876567987957852
1997	21.858190709046454
1998	14.783759929390996
1999	9.233610341643583
2000	12.46278179498086
2001	11.984126984126984
2002	13.01526717557252
2003	16.341991341991342
2004	16.73511293634497
2005	20.419534578826614
2006	20.229738353541798
2007	19.45137157107232
2008	19.637012793811365
2009	22.29944975383724
2010	23.230390817163162
2011	22.384937238493723
2012	32.423716199454226
2013	41.35861737878061
2014	44.9842555105713
2015	43.61214238916794