|
| year | consumption | change |
| 1980 | .05 | NA |
| 1981 | .07 | 39.80 % |
| 1982 | .06 | -22.16 % |
| 1983 | .06 | -4.36 % |
| 1984 | .02 | -65.58 % |
| 1985 | .01 | -50.76 % |
| 1986 | .02 | 66.38 % |
| 1987 | .01 | -30.63 % |
| 1988 | .01 | 3.78 % |
| 1989 | .01 | -4.88 % |
| 1990 | .03 | 142.20 % |
| 1991 | .03 | 13.42 % |
| 1992 | .04 | 19.31 % |
| 1993 | .05 | 32.11 % |
| 1994 | .07 | 43.26 % |
| 1995 | .05 | -24.16 % |
| 1996 | .04 | -11.10 % |
| 1997 | .05 | 14.15 % |
| 1998 | .04 | -17.47 % |
| 1999 | .05 | 11.37 % |
| 2000 | .04 | -16.43 % |
| 2001 | .04 | 7.71 % |
| 2002 | .03 | -31.88 % |
| 2003 | .03 | 14.85 % |
| 2004 | .03 | -20.54 % |
| 2005 | .03 | 11.71 % |
| 2006 | .03 | 4.08 % |
| 2007 | .03 | -10.01 % |
| 2008 | .02 | -13.30 % |
| 2009 | .01 | -38.94 % |
| 2010 | .01 | -10.50 % |
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