|
| year | production | consumption |
| 1980 | .04 | .23 |
| 1981 | .04 | .22 |
| 1982 | .04 | .22 |
| 1983 | .04 | .22 |
| 1984 | .04 | .21 |
| 1985 | .04 | .22 |
| 1986 | .04 | .25 |
| 1987 | .03 | .25 |
| 1988 | .03 | .27 |
| 1989 | .03 | .30 |
| 1990 | .03 | .31 |
| 1991 | .03 | .32 |
| 1992 | .03 | .33 |
| 1993 | .03 | .30 |
| 1994 | .03 | .39 |
| 1995 | .03 | .37 |
| 1996 | .04 | .40 |
| 1997 | .04 | .41 |
| 1998 | .03 | .42 |
| 1999 | .02 | .44 |
| 2000 | .01 | .45 |
| 2001 | .01 | .48 |
| 2002 | .01 | .49 |
| 2003 | .02 | .49 |
| 2004 | .02 | .49 |
| 2005 | .01 | .50 |
| 2006 | .01 | .52 |
| 2007 | .01 | .53 |
| 2008 | .02 | .60 |
| 2009 | .03 | .64 |
| 2010 | .04 | .67 |
|
|