where can i find the beta coefficient of the advertising industry?

Answer 1

Beta can be computed a number of different ways. Even at the company level, various web sites report "Beta", but one might be a 1-year computation, another a 3-year computation, and yet another a 5-year computation.

However, one source:

http://pages.stern.nyu.edu/~adamodar/New_Home_Page/datafile/Betas.html

Or, as a industry comparison number to an individual company:

http://www.investor.reuters.wallst.com/stocks/Ratios.asp?ticker=OMC