Year	% of total
1960	92.08906058672369
1961	90.91027364586496
1962	87.96845669080182
1963	84.17860327610724
1964	83.15781818181817
1965	80.22119114420222
1966	81.22419116826428
1967	79.19670260137312
1968	75.45580959873243
1969	77.08265105616505
1970	75.47873152850434
1971	73.23572236772708
1972	73.79889244170693
1973	72.07245233837256
1974	74.30541593919193
1975	73.07275877003032
1976	71.31949567433439
1977	68.36311353741623
1978	68.60577357709234
1979	67.97944919384032
1980	67.28175783196438
1981	68.12861752804385
1982	66.55367640035213
1983	65.21148517764756
1984	65.47287247431409
1985	66.16685697351103
1986	66.30727590196338
1987	63.71935000241814
1988	60.77736350373044
1989	58.33183174164615
1990	61.558456645803986
1991	60.626872070817626
1992	60.809296550504634
1993	60.805424370956004
1994	59.35757180931951
1995	59.98571441326417
1996	62.07523096230074
1997	61.139818688981876
1998	59.092066397340695
1999	59.72294432113586
2000	59.19936723492229
2001	56.515819458103024
2002	58.313122340549405
2003	57.23850039522206
2004	56.81861752227585
2005	58.32489960098239
2006	57.74160186421595
2007	58.47559142299451
2008	59.73576676067394
2009	60.46978159420646
2010	58.18440157918444
2011	59.040234346761544
2012	59.72330209172686
2013	58.88807882810092
2014	57.254616655888476
2015	56.74419298088679