Year	% of total
1960	10.192345154104803
1961	9.436814817746468
1962	8.309111174246564
1963	7.4999665000602995
1964	6.771992467411773
1965	8.319286068418444
1966	8.945965373012683
1967	8.346234355239632
1968	7.727279473238976
1969	5.8395265681983135
1970	5.676375048174861
1971	4.111548087236325
1972	3.816052341701336
1973	4.069164850194469
1974	4.516556867906074
1975	4.443546916121635
1976	3.286009543854987
1977	4.124604215907411
1978	4.098005687830097
1979	3.9302953763369572
1980	4.089076639361839
1981	4.2555966280195925
1982	4.216325684829815
1983	3.9225267926427723
1984	3.6710629072417746
1985	3.3369832488089752
1986	3.557979582724079
1987	3.8336032213125417
1988	3.6674593179786843
1989	3.268585945026615
1990	3.1819592805624026
1991	2.7790738038094456
1992	3.2598674841475663
1993	3.421711927760882
1994	3.7947087327805336
1995	4.087730427503781
1996	3.987172479666455
1997	3.167272189791811
1998	3.116723240552161
1999	3.555728492701952
2000	3.7972228483364874
2001	3.9067789910738533
2002	3.9735099337748347
2003	2.9358701000492045
2004	3.2884692483288473
2005	3.1890224098733357
2006	3.1621602827105315
2007	3.340734743862274
2008	3.2225164727765696
2009	3.2257791126946302
2010	3.3440102907356244
2011	2.910109546990587
2012	3.487954492254512
2013	3.6334910616246274
2014	3.1493492920516197
2015	2.960682843266502