|
| year | production | consumption |
| 1980 | | 1.90 |
| 1981 | | 2.00 |
| 1982 | | 2.25 |
| 1983 | | 2.46 |
| 1984 | | 2.75 |
| 1985 | | 2.79 |
| 1986 | | 2.91 |
| 1987 | | 2.93 |
| 1988 | | 3.03 |
| 1989 | | 3.03 |
| 1990 | | 3.03 |
| 1991 | | 3.12 |
| 1992 | | 3.20 |
| 1993 | | 3.20 |
| 1994 | | 3.28 |
| 1995 | | 10.28 |
| 1996 | | 11.36 |
| 1997 | | 13.30 |
| 1998 | | 15.98 |
| 1999 | | 16.41 |
| 2000 | | 17.46 |
| 2001 | | 20.47 |
| 2002 | | 21.94 |
| 2003 | | 23.74 |
| 2004 | | 26.46 |
| 2005 | | 28.02 |
| 2006 | | 30.97 |
| 2007 | | 33.20 |
| 2008 | | 34.34 |
| 2009 | | 32.30 |
| 2010 | | 26.25 |
| 2011 | | |
|
|