|
| year | consumption | change |
| 1980 | .46 | NA |
| 1981 | .46 | 1.68 % |
| 1982 | .50 | 8.06 % |
| 1983 | .46 | -8.31 % |
| 1984 | .48 | 3.49 % |
| 1985 | .48 | 1.75 % |
| 1986 | .50 | 3.46 % |
| 1987 | .49 | -1.61 % |
| 1988 | .50 | 1.47 % |
| 1989 | .51 | 2.05 % |
| 1990 | .50 | -1.67 % |
| 1991 | .46 | -7.75 % |
| 1992 | .41 | -11.63 % |
| 1993 | .37 | -9.33 % |
| 1994 | .41 | 11.01 % |
| 1995 | .42 | 1.77 % |
| 1996 | .43 | 2.32 % |
| 1997 | .47 | 10.16 % |
| 1998 | .45 | -4.81 % |
| 1999 | .46 | 1.62 % |
| 2000 | .46 | 0.63 % |
| 2001 | .47 | 1.36 % |
| 2002 | .47 | 0.22 % |
| 2003 | .46 | -0.74 % |
| 2004 | .52 | 12.09 % |
| 2005 | .45 | -13.21 % |
| 2006 | .36 | -21.14 % |
| 2007 | .37 | 4.67 % |
| 2008 | .36 | -3.82 % |
| 2009 | .41 | 15.83 % |
| 2010 | .40 | -3.54 % |
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