|
| year | production | consumption |
| 1980 | | .27 |
| 1981 | | .25 |
| 1982 | | .27 |
| 1983 | | .27 |
| 1984 | | .25 |
| 1985 | | .29 |
| 1986 | | .29 |
| 1987 | | .32 |
| 1988 | | .38 |
| 1989 | | .56 |
| 1990 | | .59 |
| 1991 | | .56 |
| 1992 | | .60 |
| 1993 | | .56 |
| 1994 | | .89 |
| 1995 | | .94 |
| 1996 | | .94 |
| 1997 | | 1.01 |
| 1998 | | 1.19 |
| 1999 | | 1.19 |
| 2000 | | 1.21 |
| 2001 | | 1.23 |
| 2002 | | 1.31 |
| 2003 | | 1.38 |
| 2004 | | 1.47 |
| 2005 | | 1.46 |
| 2006 | | 1.45 |
| 2007 | | 1.47 |
| 2008 | | 1.47 |
| 2009 | | 1.47 |
| 2010 | | 1.47 |
| 2011 | | |
|
|