Year	% of total
1971	10.475327092384264
1972	11.419052992445186
1973	12.455886224746335
1974	11.782130317749418
1975	11.941606276467466
1976	12.721041136628717
1977	12.577299340675763
1978	12.796774119217549
1979	12.99007733301298
1980	13.28220452112788
1981	12.549872645804106
1982	12.004379217479027
1983	12.31075981795134
1984	11.571049915917612
1985	10.389510559478081
1986	10.10806942649143
1987	9.570395670766917
1988	9.051179890086994
1989	8.557007171488738
1990	13.838060584132766
1991	13.468361170454665
1992	12.645510219415243
1993	11.916232857079168
1994	11.288669849158175
1995	11.093974417794737
1996	10.567751940898994
1997	10.442035598002564
1998	10.670097693643116
1999	9.829191361151928
2000	9.415419100567334
2001	8.606654692266726
2002	8.04666841318232
2003	7.042547453751058
2004	6.940128376277927
2005	6.117363181836671
2006	5.615188686536909
2007	5.1102025264423405
2008	4.997630486055596
2009	4.651765031795558
2010	4.2172723466488735
2011	4.436411754809385
2012	4.357991618104216
2013	4.135386329524277
2014	3.800599151764724
2015	3.4097843329744464