|
| year | production | change |
| 1980 | .24 | NA |
| 1981 | .26 | 7.18 % |
| 1982 | .27 | 3.53 % |
| 1983 | .27 | -1.18 % |
| 1984 | .27 | 2.47 % |
| 1985 | .25 | -7.31 % |
| 1986 | .25 | -2.19 % |
| 1987 | .24 | -2.81 % |
| 1988 | .24 | -1.83 % |
| 1989 | .24 | 1.62 % |
| 1990 | .22 | -10.62 % |
| 1991 | .23 | 8.56 % |
| 1992 | .25 | 7.80 % |
| 1993 | .23 | -10.88 % |
| 1994 | .21 | -6.18 % |
| 1995 | .20 | -5.10 % |
| 1996 | .22 | 7.68 % |
| 1997 | .25 | 13.61 % |
| 1998 | .25 | 0.91 % |
| 1999 | .25 | 2.38 % |
| 2000 | .25 | -3.07 % |
| 2001 | .24 | -1.01 % |
| 2002 | .25 | 3.62 % |
| 2003 | .26 | 1.83 % |
| 2004 | .27 | 5.41 % |
| 2005 | .26 | -2.33 % |
| 2006 | .27 | 0.91 % |
| 2007 | .24 | -8.53 % |
| 2008 | .24 | -2.72 % |
| 2009 | .27 | 11.91 % |
| 2010 | .26 | -2.63 % |
|
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