Annual % of total
1960 40.73743016759776
1961 39.512882447665056
1962 39.664277631082605
1963 38.675176815594284
1964 35.523648648648646
1965 31.453292741547827
1966 27.33655796536121
1967 32.225519287833826
1968 29.937973811164714
1969 30.383056608707022
1970 20.46217402530338
1971 21.451027811366384
1972 21.269656377402445
1973 23.068552774755165
1974 22.798552472858866
1975 24.476453161712126
1976 24.222585924713584
1977 23.937756243011556
1978 23.761766517110935
1979 25.352810101510276
1980 23.239087301587304
1981 24.001979544704717
1982 23.951761041450364
1983 24.56803856136448
1984 24.511492101519803
1985 25.25581747896612
1986 24.540702016430174
1987 24.70947123765253
1988 23.94769962243043
1989 24.378315078873047
1990 28.436887024150636
1991 24.56266508501384
1992 25.705525277203535
1993 25.48755647185371
1994 24.14124579124579
1995 23.95409075516424
1996 21.279192863211556
1997 19.341276930334956
1998 18.252036199095024
1999 17.347200644352963
2000 17.579177258673994
2001 17.639923155737705
2002 16.434242424242427
2003 18.590289182434848
2004 12.960385983635717
2005 17.685945432567777
2006 16.213069993069993
2007 13.617276566987666
2008 17.962188333333334
2009 18.76017630241423
2010 20.846566171923314
2011 19.732876555571448
2012 16.433418693982073
2013 16.88073916955907
2014 18.321217739914808
2015 23.645655929902507
2016 23.247098853868195