Year % of output 1971 8.823529411764707 1972 11.48936170212766 1973 13.716814159292035 1974 13.292682926829269 1975 14.17233560090703 1976 14.383561643835616 1977 14.100346020761245 1978 12.214411247803165 1979 13.472070098576122 1980 15.124378109452735 1981 13.78640776699029 1982 15.06986027944112 1983 19.70387243735763 1984 13.704496788008566 1985 14.437984496124031 1986 15.50712489522213 1987 15.884194053208137 1988 15 1989 16.677357280307888 1990 16.815374056280028 1991 21.366954213669544 1992 21.53752287980476 1993 22.247838616714695 1994 26.746849942726232 1995 27.008086253369274 1996 26.191670847967885 1997 25.330073349633253 1998 26.301853486319505 1999 27.008310249307478 2000 30.45512547851978 2001 30.51587301587302 2002 30.15267175572519 2003 29.545454545454547 2004 27.960301163586585 2005 27.04031465093412 2006 26.96234843650287 2007 22.100997506234414 2008 21.27343052662898 2009 20.561830292499277 2010 18.474993167532112 2011 17.625523012552303 2012 15.926569089555942 2013 15.434469515122421 2014 20.82771030139451