|
| year | production | consumption |
| 1980 | .66 | .70 |
| 1981 | .67 | .72 |
| 1982 | .75 | .77 |
| 1983 | .79 | .78 |
| 1984 | .93 | .85 |
| 1985 | 1.02 | .86 |
| 1986 | 1.39 | .90 |
| 1987 | 1.56 | .82 |
| 1988 | 1.62 | .92 |
| 1989 | 1.78 | .95 |
| 1990 | 1.93 | .89 |
| 1991 | 1.87 | .97 |
| 1992 | 1.90 | .98 |
| 1993 | 1.99 | 1.00 |
| 1994 | 2.01 | 1.10 |
| 1995 | 2.38 | 1.09 |
| 1996 | 2.62 | 1.19 |
| 1997 | 2.84 | 1.23 |
| 1998 | 3.05 | 1.24 |
| 1999 | 3.20 | 1.18 |
| 2000 | 3.08 | 1.17 |
| 2001 | 3.08 | 1.16 |
| 2002 | 2.89 | 1.16 |
| 2003 | 3.12 | 1.20 |
| 2004 | 3.23 | 1.22 |
| 2005 | 3.38 | 1.27 |
| 2006 | 3.61 | 1.31 |
| 2007 | 3.76 | 1.33 |
| 2008 | 4.04 | 1.34 |
| 2009 | 4.20 | 1.34 |
| 2010 | 4.51 | 1.37 |
|
|