|
| year | consumption | change |
| 1980 | .11 | NA |
| 1981 | .10 | -5.20 % |
| 1982 | .10 | -4.99 % |
| 1983 | .12 | 22.11 % |
| 1984 | .12 | -2.66 % |
| 1985 | .11 | -7.35 % |
| 1986 | .11 | 4.92 % |
| 1987 | .12 | 6.91 % |
| 1988 | .12 | -2.38 % |
| 1989 | .10 | -11.83 % |
| 1990 | .13 | 28.09 % |
| 1991 | .12 | -10.80 % |
| 1992 | .14 | 14.39 % |
| 1993 | .13 | -4.92 % |
| 1994 | .14 | 6.37 % |
| 1995 | .12 | -9.87 % |
| 1996 | .13 | 3.29 % |
| 1997 | .14 | 10.09 % |
| 1998 | .18 | 25.15 % |
| 1999 | .16 | -10.03 % |
| 2000 | .16 | 2.97 % |
| 2001 | .16 | -1.38 % |
| 2002 | .17 | 3.85 % |
| 2003 | .16 | -3.02 % |
| 2004 | .14 | -13.72 % |
| 2005 | .16 | 11.23 % |
| 2006 | .15 | -5.10 % |
| 2007 | .18 | 19.50 % |
| 2008 | .18 | 3.78 % |
| 2009 | .19 | 2.74 % |
| 2010 | .21 | 11.58 % |
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