Year % of output 1960 11.56002695811071 1961 10.868309469673692 1962 10.579628912682958 1963 9.627431921466048 1964 9.345926263086026 1965 9.162165024891431 1966 8.674871458681922 1967 7.9690015146061 1968 7.800013492710869 1969 7.3210320638330355 1970 7.113237868396132 1971 7.332755044314539 1972 7.301927895455773 1973 7.462305325934454 1974 6.529015388698571 1975 6.954459224747307 1976 6.83258938151852 1977 6.778551934435273 1978 6.619453678277208 1979 6.491399009913969 1980 6.431587001954522 1981 6.638072406538977 1982 6.505285910468622 1983 6.530139603322359 1984 6.236047735669935 1985 6.4242367640460385 1986 6.448986333470545 1987 6.407916088885497 1988 6.060779240667306 1989 6.207293039733367 1990 6.161811907221111 1991 6.282656662626504 1992 6.323667436144696 1993 6.555550473994933 1994 6.116401601252242 1995 6.5562988713728165 1996 6.459824927052939 1997 6.3556013945602965 1998 6.386860002630549 1999 6.3480402929252975 2000 6.252610936568394 2001 6.3727339430601235 2002 6.51552626879656 2003 6.2788740861786225 2004 6.158648509589974 2005 6.248892368547284 2006 6.098138793415669 2007 5.940662225488333 2008 5.900065941504256 2009 5.840706534650019 2010 5.82359840342839 2011 5.701272535453556 2012 5.6142562435355465 2013 5.6088151877910635 2014 5.41234149650027