That number is taken from the anna.aero airport passenger stats database, which is generally very accurate in terms of Irish passenger numbers.
They state that there were 92,147 passengers in January 2011, a drop of 37.4% from January 2010 when Ryanair still had a large presence at the airport. January 2012 figures are then given as 76,805, a drop of 16.6% on the January 2011 numbers.
Where was the 2% drop quoted? Maybe one number includes troop movements and the other does not?