Year	% of total
1960	30.88181660907762
1961	30.24832247944685
1962	28.905478804395766
1963	27.979050741592904
1964	26.58139080121376
1965	27.320607843392423
1966	26.767485048809426
1967	25.864826099739236
1968	24.32336336350618
1969	23.379944875560824
1970	21.977997911653937
1971	21.7168919994018
1972	20.964995968016005
1973	19.448200982490935
1974	21.307414449585092
1975	20.986141657121276
1976	18.794231536913383
1977	18.137000628960102
1978	18.64876105023371
1979	18.818448877493232
1980	18.230771411773556
1981	18.1841248477347
1982	18.85413266947876
1983	19.105749365772663
1984	18.163338024473866
1985	17.342970014890867
1986	17.079074744181
1987	16.127779288003836
1988	15.493553831015353
1989	14.346222568716794
1990	14.638056165595156
1991	14.848977769134306
1992	14.496165686904158
1993	15.049598277099484
1994	14.31985618739925
1995	14.80654723195942
1996	14.802681827361159
1997	14.631148001416653
1998	13.955308387305992
1999	13.68389830684807
2000	13.352985766328537
2001	12.564238409076395
2002	12.5686908270921
2003	12.272637177065723
2004	12.169129126627979
2005	11.964773813713556
2006	12.014293222069355
2007	11.557711725103767
2008	11.941395665837309
2009	12.459907351719913
2010	12.001642066959965
2011	12.37928669701635
2012	12.426316525577153
2013	12.764207737068745
2014	12.680764580647866
2015	12.249493487737915