Does an economics degree qualify for the 17 month OPT extension?
CIP codes in economics include:

45.0601) Economics, General.

45.0602) Applied Economics.

45.0603) Econometrics and Quantitative Economics.

45.0604) Development Economics and International Development.

45.0605) International Economics.

45.0699) Economics, Other.

Your registrar's office should be able to tell you what the CIP code is for the degree program that you're in.  I would expect the list that you have referenced to include other codes if they were approved for OPT.