Hi I am writing a paper for school about the costs invovled with producing as well as the revenues generated by the PC & video games industry since its inception. I was just wondering if anyone knows of some reputable sources from which I can I attain this information. Any information would be greatly appreciated.

You can find a list of reputable sources here... Market Research list but almost all of them charge for their data because it costs a lot to compile it.

My article on game finances might be useful.
http://www.sloperama.com/advice/finances.htm

Thanks guys!