|
| year | production | consumption |
| 1980 | 1.38 | 370.91 |
| 1981 | 1.13 | 341.18 |
| 1982 | 1.09 | 281.53 |
| 1983 | .64 | 296.93 |
| 1984 | 1.31 | 306.32 |
| 1985 | 1.41 | 305.72 |
| 1986 | .92 | 272.38 |
| 1987 | .99 | 303.71 |
| 1988 | .60 | 298.59 |
| 1989 | .49 | 332.17 |
| 1990 | .42 | 340.61 |
| 1991 | .32 | 363.32 |
| 1992 | .21 | 374.44 |
| 1993 | .14 | 391.85 |
| 1994 | .04 | 400.65 |
| 1995 | | 443.24 |
| 1996 | .07 | 492.68 |
| 1997 | | 469.97 |
| 1998 | | 517.58 |
| 1999 | | 551.06 |
| 2000 | .07 | 553.85 |
| 2001 | | 546.78 |
| 2002 | | 563.52 |
| 2003 | | 600.36 |
| 2004 | | 611.80 |
| 2005 | | 601.41 |
| 2006 | | 619.04 |
| 2007 | | 623.66 |
| 2008 | | 619.43 |
| 2009 | | 625.50 |
| 2010 | | 699.73 |
| 2011 | | 596.19 |
|
|