Chart 2 
The 12-month change in the natural gas index

Chart description

The title of the graph is "The 12-month change in the natural gas index."
This is a line chart.
There are in total 61 categories in the horizontal axis. The vertical axis starts at -40 and ends at 35 with ticks every 10 points.
There are 1 series in this graph.
The vertical axis is "12-month % change."
The units of the horizontal axis are months by year from May 2008 to May 2013.
The title of series 1 is "Natural gas index."
The minimum value is -38.1 occurring in August 2009.
The maximum value is 31.7 occurring in August 2008.