Monthly Summary        
   
  Year Mean Difference
  2009 2010   2009 2010
January 4134 5434 4824 -690 609
February 11175 14684 13039 -1864 1645
March 19990 26909 23029 -3039 3881
April 28971 37125 32006 -3035 5119
May 41004 50723 44105 -3101 6618
June 51249 61213 53888 -2639 7325
July 64873 74596 67130 -2257 7467
August 76200 85971 78545 -2345 7425
September 84975 94052 86759 -1784 7293
October 99468 108248 100532 -1064 7716
November 106969 115670 107438 -468 8233
December 121544 130433 121064 480 9368