Annual % of total
1960 66.8648401446805
1961 66.25647668393782
1962 64.83406096665766
1963 63.13019491125549
1964 61.65416063797571
1965 58.79107554262155
1966 59.38442785311595
1967 58.38132251567332
1968 56.93506210503377
1969 54.858998814249624
1970 50.37013116057234
1971 48.648648648648646
1972 49.400423778145154
1973 46.656658803345486
1974 49.47449044721501
1975 49.47252105745976
1976 51.04488919755035
1977 51.259519625073224
1978 51.562897077509525
1979 52.37379968885789
1980 53.493471543905116
1981 52.631327602674304
1982 52.78252016602709
1983 54.3946283348816
1984 54.12275263484191
1985 56.29484373099841
1986 56.07817967878482
1987 57.597972537621175
1988 57.67885979077442
1989 58.29383886255924
1990 54.249620257966626
1991 55.745437270975785
1992 56.35778357430318
1993 55.977086209428705
1994 54.239808016650514
1995 53.00471436974499
1996 55.43891017724224
1997 56.676708283078526
1998 56.58411768296404
1999 56.94838668027865
2000 56.07162391901066
2001 56.10629058441559
2002 56.124666893366204
2003 53.8199627830336
2004 53.70543214608372
2005 54.86556845552217
2006 55.8301874366768
2007 53.81603446038872
2008 53.608047619047625
2009 54.479949107481964
2010 53.25788537498386
2011 51.60339813878736
2012 50.663287969515515
2013 46.09782635062093
2014 44.18978885043798
2015 45.0033372343538
2016 44.952171059485366