|
| year | production | consumption |
| 1980 | .08 | .35 |
| 1981 | .08 | .37 |
| 1982 | .01 | .37 |
| 1983 | .00 | .37 |
| 1984 | .00 | .38 |
| 1985 | .00 | .36 |
| 1986 | .00 | .37 |
| 1987 | .00 | .39 |
| 1988 | .00 | .43 |
| 1989 | .00 | .44 |
| 1990 | .00 | .45 |
| 1991 | .00 | .48 |
| 1992 | .00 | .54 |
| 1993 | .00 | .53 |
| 1994 | .00 | .62 |
| 1995 | .00 | .62 |
| 1996 | .00 | .66 |
| 1997 | .00 | .71 |
| 1998 | .00 | .73 |
| 1999 | .00 | .74 |
| 2000 | .00 | .81 |
| 2001 | .00 | .87 |
| 2002 | .00 | .84 |
| 2003 | .00 | .85 |
| 2004 | .03 | .86 |
| 2005 | .03 | .87 |
| 2006 | .04 | .88 |
| 2007 | .04 | .91 |
| 2008 | .05 | .83 |
| 2009 | .04 | .88 |
| 2010 | .06 | .95 |
|
|