|
| year | production | consumption |
| 1980 | | 4.30 |
| 1981 | | 4.30 |
| 1982 | | 4.70 |
| 1983 | | 5.40 |
| 1984 | | |
| 1985 | | 5.91 |
| 1986 | | 5.83 |
| 1987 | | 6.39 |
| 1988 | | 7.51 |
| 1989 | | 7.96 |
| 1990 | | 8.63 |
| 1991 | | 9.91 |
| 1992 | | 10.38 |
| 1993 | | 13.14 |
| 1994 | | 13.37 |
| 1995 | | 13.26 |
| 1996 | | 13.27 |
| 1997 | | 13.37 |
| 1998 | | 17.01 |
| 1999 | | 17.01 |
| 2000 | | 17.72 |
| 2001 | | 18.53 |
| 2002 | | 18.49 |
| 2003 | | 18.50 |
| 2004 | | 18.82 |
| 2005 | | 19.20 |
| 2006 | | 19.44 |
| 2007 | | 19.74 |
| 2008 | | 19.90 |
| 2009 | | 20.51 |
| 2010 | | 20.51 |
| 2011 | | 21.00 |
|
|