Seems no one knows quite what it is…
;)

Labor Market Conditions Index

Highlights
The Fed’s Labor Market Conditions Index showed softening labor market conditions in November. The index pulls together 19 different labor market indicators. The November index posted at 2.9 versus a revised 3.9 for October. The November number is the lowest since January 2014 and suggests that the Fed will maintain loose monetary policy into 2015. The Fed only occasionally publishes details of the index since it is not an official indicator release but instead a research department number.