|
| year | consumption | change |
| 1980 | .43 | NA |
| 1981 | .45 | 5.27 % |
| 1982 | .33 | -26.45 % |
| 1983 | .32 | -3.13 % |
| 1984 | .36 | 12.05 % |
| 1985 | .31 | -13.49 % |
| 1986 | .34 | 8.49 % |
| 1987 | .35 | 3.99 % |
| 1988 | .32 | -8.70 % |
| 1989 | .31 | -2.47 % |
| 1990 | .30 | -3.89 % |
| 1991 | .37 | 24.29 % |
| 1992 | .33 | -10.85 % |
| 1993 | .31 | -7.11 % |
| 1994 | .36 | 15.21 % |
| 1995 | .36 | 2.21 % |
| 1996 | .37 | 2.89 % |
| 1997 | .38 | 2.69 % |
| 1998 | .39 | 2.40 % |
| 1999 | .33 | -16.80 % |
| 2000 | .44 | 34.58 % |
| 2001 | .48 | 8.55 % |
| 2002 | .48 | 0.68 % |
| 2003 | .52 | 7.94 % |
| 2004 | .53 | 2.03 % |
| 2005 | .51 | -3.18 % |
| 2006 | .51 | 0.15 % |
| 2007 | .43 | -17.09 % |
| 2008 | .44 | 3.38 % |
| 2009 | .39 | -10.57 % |
| 2010 | .44 | 11.52 % |
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