YEAR,Jan,Feb,Mar,Apr,May,Jun,Jul,Aug,Sep,Oct,Nov,Dec,Annual 24-hr Avg.
1997,14690,15248,17858,,19788,20769,21190,21863,19418,18771,17704,16409
1998,14663,16365,18312,19428,,22292,21679,22475,20437,19703,18172,16604
1999,15894,16241,19319,19404,19993,22917,22938,23706,21318,20221,18521,17047,19793
2000,15491,17694,19812,19956,21114,22876,23610,25022,21291,20548,19047,16734,20266
2001,15796,17533,20202,20134,20781,23011,23272,23848,21392,20495,19373,16706,20212
2002,15959,18571,20225,20226,21971,23628,23646,24251,20416,20784,20230,17725,20636
2003,16858,17871,19635,19612,21200,23479,23674,24302,21073,20917,19124,17666,20451
2004,15803,17484,20771,20571,21450,21378,,22345,20978,,19222,18425
2005,16199,18320,20574,20420,20909,23135,23698,23232,21151,20368,19361,17700,20422
2006,16721
2007,,,,,23100,24297,24674,25684,22601,22230,21266,18268
2008,,,21070,19766,20931,21731,21834,22537,19965,19648,18788,16084
2009,15580,17460,19490,19996,21317,22240,23170,22852,21051