While no theory is perfect this one helped me make sense of Maslov's, which was obviously too rigid. The ERG explains people will sacrifice their existance needs for the good of the group or personal growth (self actualization), which is helpful in understanding terrorist/insurgent motivation. You will not get them to quit fighting by simply providing economic aid, that isn't the real issue.

http://www.netmba.com/mgmt/ob/motivation/erg/


How the existence, relatedness, and growth theory differs from Maslow's hierarchy:

ERG allows different levels of needs to be pursued simultaneously.

Allows the order of needs to be different for different people.

If a higher level need is unfullfilled the person "may" regress to a lower level.

Bottom line it is not a rigid hierarchy, and explains a wider range of behaviors, such as the "starving artist" who may place growth above existence needs.
(this is paraphrased)

The best part of this theory to me is it refutes Maslov's, which all of us who have been in the real world outside a labatory know just doesn't apply to the behavior we see.