|
| year | production | consumption |
| 1980 | | 2.80 |
| 1981 | | 3.29 |
| 1982 | | 4.56 |
| 1983 | | 2.89 |
| 1984 | | 3.30 |
| 1985 | | 3.11 |
| 1986 | | 3.20 |
| 1987 | | 3.26 |
| 1988 | | 3.21 |
| 1989 | | 3.70 |
| 1990 | | 3.85 |
| 1991 | | 3.85 |
| 1992 | | 3.94 |
| 1993 | | 3.93 |
| 1994 | | 3.83 |
| 1995 | | 3.77 |
| 1996 | | 3.82 |
| 1997 | | 3.83 |
| 1998 | | 3.83 |
| 1999 | | 3.83 |
| 2000 | | 3.74 |
| 2001 | | 3.75 |
| 2002 | | 3.82 |
| 2003 | | 3.82 |
| 2004 | | 3.81 |
| 2005 | | 4.07 |
| 2006 | | 4.14 |
| 2007 | | 4.44 |
| 2008 | | 2.70 |
| 2009 | | 4.14 |
| 2010 | | 2.00 |
| 2011 | | |
|
|