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| Month | 1988 | 1989 | 1990 | 1991 | 1992 | 1997 | 1998 | 2005 | 2006 | 2007 | 2008 | 2009 | 2010 | 2011 | 2012 |
| January | | 244.00 | 7.00 | 154.00 | 153.00 | | | | | | 12.09 | 10.00 | | | 378.04 |
| February | | 5.00 | 156.00 | 250.00 | 183.00 | | | | 26.14 | | | 24.00 | | | 132.56 |
| March | 43.00 | 250.00 | 438.00 | 481.00 | 224.00 | 74.60 | | | 41.33 | 115.76 | 71.45 | 32.63 | | 16.45 | |
| April | 369.00 | 346.00 | 614.00 | 565.00 | | 12.30 | 26.10 | | 276.84 | 147.28 | 174.76 | 22.08 | 21.10 | 313.81 | |
| May | 350.00 | 363.00 | 832.00 | 483.00 | | 112.31 | 29.36 | 40.10 | 182.76 | 516.31 | 261.90 | 175.29 | 50.56 | 658.69 | |
| June | 579.00 | 551.00 | 966.00 | 372.00 | | 133.12 | 156.56 | 145.18 | 95.93 | 1,017.73 | 190.57 | 99.58 | 26.23 | 695.94 | |
| July | 1,027.00 | 1,112.00 | 1,173.00 | 574.00 | | 113.85 | | 100.57 | 535.73 | 732.99 | 404.32 | 105.17 | | 1,329.88 | |
| August | 735.00 | 719.00 | 767.00 | 421.00 | | | | | 105.98 | 288.52 | 146.95 | 198.11 | | 635.71 | |
| September | 513.00 | 73.00 | 559.00 | 272.00 | | | 13.40 | | 164.84 | 334.01 | 239.12 | | | 241.79 | |
| October | 427.00 | 485.00 | 263.00 | 162.00 | | | | | 22.32 | 131.89 | 24.78 | | | 703.72 | |
| November | 203.00 | 140.00 | 236.00 | 105.00 | | | | | | 51.76 | 62.77 | | | 458.18 | |
| December | 188.00 | 100.00 | 108.00 | 153.00 | | | | | | | | | | 215.70 | |
| | 4,434.00 | 4,388.00 | 6,119.00 | 3,992.00 | 560.00 | 446.18 | 225.42 | 285.85 | 1,451.87 | 3,336.25 | 1,588.71 | 666.86 | 97.89 | 5,269.87 | 510.60 |
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