Americans used less energy 2012

Hi all,
Here's what I was referring to today in class:
http://thinkprogress.org/climate/2013/10/22/2814191/carbon-dioxide-emissions-energy-drop-2012/

"The drop in 2009 was largely due to the contraction in the U.S. economy during the Great Recession, yet the falling carbon dioxide emissions in 2012 occurred while GDP rose 2.8 percent. Energy consumption fell by 2.8 percent."

Which part of the I=PAT equation must have changed, then? The next paragraph gets at it:
"The main reason for this is that American energy intensity dropped — energy use per dollar of GDP fell 6.5 percent. The economy was able to do more with less energy, which has been a long-term trend ever since an inefficient high in 1970."

An important thing to note, though, is that this is ONLY the emissions from energy use. We have a lot of other emissions (e.g., from land use change, agriculture, etc), that aren't accounted for in this analysis. 
Enjoy,
Sarah