|
| year | production | consumption |
| 1980 | .13 | .17 |
| 1981 | .15 | .17 |
| 1982 | .16 | .18 |
| 1983 | .16 | .19 |
| 1984 | .13 | .19 |
| 1985 | .15 | .21 |
| 1986 | .16 | .19 |
| 1987 | .18 | .22 |
| 1988 | .19 | .20 |
| 1989 | .23 | .24 |
| 1990 | .28 | .26 |
| 1991 | .36 | .28 |
| 1992 | .43 | .29 |
| 1993 | .50 | .33 |
| 1994 | .55 | .37 |
| 1995 | .72 | .48 |
| 1996 | .78 | .57 |
| 1997 | .81 | .58 |
| 1998 | .95 | .61 |
| 1999 | 1.04 | .68 |
| 2000 | 1.16 | .74 |
| 2001 | 1.32 | .81 |
| 2002 | 1.38 | .90 |
| 2003 | 1.46 | .98 |
| 2004 | 1.77 | 1.07 |
| 2005 | 1.97 | 1.17 |
| 2006 | 2.11 | 1.31 |
| 2007 | 2.16 | 1.42 |
| 2008 | 2.14 | 1.64 |
| 2009 | 2.31 | 1.68 |
| 2010 | 2.32 | 1.86 |
|
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