|
| year | consumption | change |
| 1980 | .25 | NA |
| 1981 | .22 | -10.36 % |
| 1982 | .16 | -27.40 % |
| 1983 | .11 | -29.70 % |
| 1984 | .13 | 16.93 % |
| 1985 | .15 | 11.93 % |
| 1986 | .10 | -33.38 % |
| 1987 | .12 | 17.73 % |
| 1988 | .08 | -30.03 % |
| 1989 | .13 | 52.36 % |
| 1990 | .12 | -7.29 % |
| 1991 | .12 | 2.41 % |
| 1992 | .12 | 2.16 % |
| 1993 | .09 | -29.88 % |
| 1994 | .12 | 44.47 % |
| 1995 | .12 | -0.85 % |
| 1996 | .12 | -1.07 % |
| 1997 | .12 | 2.07 % |
| 1998 | .13 | 3.67 % |
| 1999 | .31 | 140.18 % |
| 2000 | .14 | -54.74 % |
| 2001 | .19 | 38.45 % |
| 2002 | .19 | -0.63 % |
| 2003 | .22 | 17.74 % |
| 2004 | .23 | 4.45 % |
| 2005 | .23 | -2.43 % |
| 2006 | .24 | 4.38 % |
| 2007 | .22 | -9.58 % |
| 2008 | .22 | 3.25 % |
| 2009 | .22 | 0.07 % |
| 2010 | .23 | 2.21 % |
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