|
| year | production | consumption |
| 1980 | | |
| 1981 | | |
| 1982 | | |
| 1983 | | |
| 1984 | | |
| 1985 | | |
| 1986 | | |
| 1987 | | |
| 1988 | | |
| 1989 | | |
| 1990 | | |
| 1991 | | |
| 1992 | .10 | 1.53 |
| 1993 | .10 | 1.24 |
| 1994 | .10 | 1.08 |
| 1995 | .09 | 1.01 |
| 1996 | .09 | 1.01 |
| 1997 | .09 | 1.00 |
| 1998 | .09 | .98 |
| 1999 | .09 | .99 |
| 2000 | .09 | 1.05 |
| 2001 | .09 | .96 |
| 2002 | .09 | .91 |
| 2003 | .08 | .98 |
| 2004 | .09 | .95 |
| 2005 | .08 | 1.12 |
| 2006 | .08 | 1.15 |
| 2007 | .08 | 1.15 |
| 2008 | .08 | 1.12 |
| 2009 | .08 | 1.05 |
| 2010 | .07 | 1.13 |
|
|