|
| year | production | consumption |
| 1984 | | |
| 1985 | | |
| 1986 | | 3.39 |
| 1987 | | 3.39 |
| 1988 | | 3.38 |
| 1989 | | 4.28 |
| 1990 | .06 | 4.66 |
| 1991 | .06 | 3.98 |
| 1992 | .06 | 4.50 |
| 1993 | .06 | 5.36 |
| 1994 | .06 | 5.99 |
| 1995 | .06 | 6.84 |
| 1996 | .06 | 6.91 |
| 1997 | .06 | 6.31 |
| 1998 | .06 | 5.59 |
| 1999 | | 6.01 |
| 2000 | | 5.81 |
| 2001 | | 10.80 |
| 2002 | | 8.39 |
| 2003 | | 7.35 |
| 2004 | | 7.60 |
| 2005 | | 7.05 |
| 2006 | | 6.52 |
| 2007 | | 4.66 |
| 2008 | | 2.23 |
| 2009 | | .49 |
| 2010 | | 1.86 |
|
|