Probably a change in your credit rating. Card usage has declined since 2008 partly due to the economy and partly due to changes in the laws.
A good slow moving indicator of the condition of the economy is the Capacity Utilization: Total Industry (TCU) number put out monthly by the St. Louis Fed. The gray vertical areas on the chart at the link below are recessionary periods and you can see that the number tracks the economy very accurately.
http://research.stlouisfed.org/fred2/series/TCU