These polls from a Singaporean forum might help answer your question:

http://forum.clubsnap.org/showthread.php?t=257616

http://forum.clubsnap.org/showthread.php?t=110914

There was another poll in those forums whereby photogs were asked if they should be raising their rates. Most answered yes - not sure if this is an indication that they are not earning enough, or that they know there is room to profit some more. Can't seem to local that poll though.

There are also misc problems about earnings, like not getting paid, paid late, customer argue your work is bad and pay partially, and copyright issues of photos you take while under employment.