|
| year | production | consumption |
| 1980 | 1.20 | .21 |
| 1981 | 1.05 | .20 |
| 1982 | .93 | .24 |
| 1983 | .84 | .22 |
| 1984 | 1.09 | .27 |
| 1985 | .88 | .24 |
| 1986 | .88 | .26 |
| 1987 | .86 | .26 |
| 1988 | .99 | .27 |
| 1989 | 1.06 | .28 |
| 1990 | 1.20 | .34 |
| 1991 | 1.25 | .40 |
| 1992 | 1.39 | .47 |
| 1993 | 1.45 | .53 |
| 1994 | 1.44 | .56 |
| 1995 | 1.51 | .56 |
| 1996 | 1.66 | .58 |
| 1997 | 1.90 | .61 |
| 1998 | 2.31 | .62 |
| 1999 | 2.37 | .59 |
| 2000 | 2.82 | .64 |
| 2001 | 2.71 | .50 |
| 2002 | 2.74 | .53 |
| 2003 | 2.95 | .58 |
| 2004 | 3.45 | .71 |
| 2005 | 3.92 | .89 |
| 2006 | 4.17 | .95 |
| 2007 | 4.62 | .99 |
| 2008 | 5.33 | 1.01 |
| 2009 | 5.82 | 1.09 |
| 2010 | 6.55 | 1.10 |
|
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