|
| year | production | consumption |
| 1980 | | |
| 1981 | | |
| 1982 | | |
| 1983 | | |
| 1984 | | |
| 1985 | | |
| 1986 | | |
| 1987 | | |
| 1988 | | |
| 1989 | | |
| 1990 | | |
| 1991 | | |
| 1992 | .03 | .20 |
| 1993 | .04 | .15 |
| 1994 | .04 | .13 |
| 1995 | .02 | .13 |
| 1996 | .04 | .17 |
| 1997 | .03 | .15 |
| 1998 | .03 | .15 |
| 1999 | .04 | .16 |
| 2000 | .03 | .16 |
| 2001 | .03 | .16 |
| 2002 | .04 | .16 |
| 2003 | .04 | .18 |
| 2004 | .05 | .18 |
| 2005 | .05 | .20 |
| 2006 | .05 | .20 |
| 2007 | .05 | .22 |
| 2008 | .04 | .22 |
| 2009 | .05 | .20 |
| 2010 | .05 | .21 |
|
|