|
| year | production | consumption |
| 1980 | | .70 |
| 1981 | | .76 |
| 1982 | | .76 |
| 1983 | | .74 |
| 1984 | | .76 |
| 1985 | | .79 |
| 1986 | | .79 |
| 1987 | | .81 |
| 1988 | | 1.86 |
| 1989 | | 1.89 |
| 1990 | | 1.94 |
| 1991 | | 2.05 |
| 1992 | | 2.10 |
| 1993 | | 2.00 |
| 1994 | | 2.17 |
| 1995 | | 2.35 |
| 1996 | | 2.36 |
| 1997 | | 2.37 |
| 1998 | | 2.41 |
| 1999 | | 2.41 |
| 2000 | | 2.39 |
| 2001 | | 2.41 |
| 2002 | | 2.41 |
| 2003 | | 2.50 |
| 2004 | | 2.70 |
| 2005 | | 2.82 |
| 2006 | | 3.19 |
| 2007 | | 3.70 |
| 2008 | | 4.49 |
| 2009 | | 3.73 |
| 2010 | | 3.75 |
| 2011 | | |
|
|