|
| year | production | consumption |
| 1980 | | .02 |
| 1981 | | .02 |
| 1982 | | .02 |
| 1983 | | .02 |
| 1984 | | .02 |
| 1985 | | .02 |
| 1986 | | .02 |
| 1987 | | .04 |
| 1988 | | .04 |
| 1989 | | .04 |
| 1990 | | .04 |
| 1991 | | .02 |
| 1992 | | .02 |
| 1993 | | .04 |
| 1994 | | .04 |
| 1995 | | .04 |
| 1996 | | .04 |
| 1997 | | .04 |
| 1998 | | .04 |
| 1999 | | .04 |
| 2000 | | .16 |
| 2001 | | .09 |
| 2002 | | .09 |
| 2003 | | .09 |
| 2004 | | .06 |
| 2005 | | .09 |
| 2006 | | .08 |
| 2007 | | .08 |
| 2008 | | .07 |
| 2009 | | .06 |
| 2010 | | .06 |
| 2011 | | |
|
|