Year	% of total
1960	1.3723696248856359
1961	1.4827018121911038
1962	1.4979338842975207
1963	1.7257248044178557
1964	0.41485169052063886
1965	4.438250428816467
1966	3.5835871707579283
1967	3.229061553985873
1968	3.6503362151777137
1969	4.084014002333722
1970	2.5006722237160526
1971	1.8110435663627154
1972	1.2782805429864252
1973	2.042483660130719
1974	1.6846045858680394
1975	2.205401364358471
1976	2.2894684451522993
1977	1.6987295825771325
1978	1.589149941776834
1979	1.6009928637914985
1980	2.104432460870709
1981	2.2497106481481484
1982	2.2986260337305464
1983	2.243394449675954
1984	1.9432143787444647
1985	2.9133439659755447
1986	2.9812564569292075
1987	3.054270506889519
1988	2.912578055307761
1989	2.595013503463932
1990	2.452191094488745
1991	2.7415231431646934
1992	3.0111737501265905
1993	2.9590190383994837
1994	3.1435501372311228
1995	3.1589427950760323
1996	2.995612633291687
1997	3.30188679245283
1998	3.0071709461022436
1999	3.1784499231020185
2000	3.562206031541086
2001	3.6973661410500775
2002	4.234392113910186
2003	4.256142387308957
2004	5.4543020947197
2005	7.640512687278081
2006	9.7167325428195
2007	13.062947799385874
2008	17.24683892248488
2009	20.223515621842285
2010	22.73192900113613
2011	24.234890533456678
2012	30.164999122345094
2013	31.149325206791467
2014	30.776188918185493
2015	30.63902810007605