|
| year | consumption | change |
| 1980 | .02 | NA |
| 1981 | .01 | -27.47 % |
| 1982 | .01 | 31.43 % |
| 1983 | .01 | -10.14 % |
| 1984 | .01 | 1.71 % |
| 1985 | .01 | 14.38 % |
| 1986 | .01 | -1.87 % |
| 1987 | .02 | 45.19 % |
| 1988 | .02 | 8.73 % |
| 1989 | .02 | -7.86 % |
| 1990 | .01 | -33.79 % |
| 1991 | .01 | 0.35 % |
| 1992 | .02 | 7.97 % |
| 1993 | .01 | -28.22 % |
| 1994 | .01 | -9.01 % |
| 1995 | .02 | 56.40 % |
| 1996 | .02 | 16.50 % |
| 1997 | .02 | 19.92 % |
| 1998 | .02 | -1.10 % |
| 1999 | .02 | 8.33 % |
| 2000 | .02 | 2.86 % |
| 2001 | .03 | 8.01 % |
| 2002 | .03 | 1.96 % |
| 2003 | .03 | -0.49 % |
| 2004 | .03 | 1.78 % |
| 2005 | .03 | 1.23 % |
| 2006 | .03 | 2.43 % |
| 2007 | .03 | 4.38 % |
| 2008 | .04 | 23.12 % |
| 2009 | .03 | -6.71 % |
| 2010 | .03 | -7.25 % |
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