Passenger on Amsterdam route:
Jan 2005 - 9,316 pax
Jan 2006 - 9,355 pax
Jan 2007 - 9,387 pax
Jan 2008 - 8,791 pax
Jan 2009 - 7,988 pax
Jan 2010 - 6,530 pax
Jan 2011 - 7,995 pax
Jan 2012 - 7,040 pax
Jan 2013 - 6,252 pax
Jan 2014 - 7,743 pax
It is clear to see how numbers fell after the autumn 2008 credit crunch. It is worth noting that the Jan 2014 figure is still below Jan 2009 and Jan 2011, so don't get too excited !
During January, KLM sometimes operate fewer rotations in the first week after 1 January. The month is also prone to weather related cancellations. Heavy rain annoys passengers but doesn't close airports like snow did in some previous years.
One should therefore be quite careful about comparing the change in weather-sensitive months between 2 years in isolation and try to look instead at the trend