Year	% of total
1960	35.59500262435223
1961	33.475573964440244
1962	30.674699052425474
1963	31.54013932419838
1964	27.41584281015244
1965	29.333271506558955
1966	30.07152043068933
1967	27.427739340720763
1968	25.949210939960466
1969	23.190315647524855
1970	21.004700837521167
1971	20.41363153114688
1972	19.843082603766042
1973	18.333723293730962
1974	19.08487882939932
1975	19.04088901335385
1976	15.198816408907282
1977	19.617093988951332
1978	18.10130519160547
1979	18.231918038631463
1980	16.816178376857437
1981	16.51421396158366
1982	16.103173794433527
1983	15.939616903828952
1984	15.447403557741751
1985	14.829046555448757
1986	13.6444810146082
1987	14.473446525132037
1988	14.973114947509192
1989	11.919913022462971
1990	12.626197788888133
1991	12.938461404607782
1992	13.547542494291974
1993	13.891915068625005
1994	14.103893622679278
1995	13.688221836554698
1996	13.286614885773517
1997	13.4112712629291
1998	13.57178643917203
1999	13.369762494877149
2000	13.369641181627786
2001	13.855689126121506
2002	11.52791179761883
2003	10.890660521649535
2004	11.262485174859341
2005	10.651526235332232
2006	10.58197534329338
2007	10.460584510261661
2008	11.013006005594539
2009	11.729425168997496
2010	12.62835703669528
2011	10.553002911918762
2012	11.37973127044801
2013	12.728010108109872
2014	13.070436200556292
2015	11.673392847304891