Specialist international gambling consultancy GBGC compiles two gambling specific stock market indices:
•    The GBGC 50: consists of the 50 largest gambling companies by their gambling market capitalisation.
•    The iGBGC: consists of the 10 largest Internet/interactive gambling companies by their gambling market capitalisation.  

GBGC 50 Index Jan 2012
GBGC tracks the rise and fall of the indices as the fortunes of the constituent gambling companies wax and wane. 
GBGC 50 Index vs iGBGC 2012
The total gambling market cap (i.e. market cap adjusted for share of revenues derived from gambling) of the 50 largest gaming companies in January 2012 decreased by 5% compared to April 2011, reaching US$185.3 billion. 
 iGBGC Index Jan 2012

Between January 2011 and January 2012 the GBGC 50 Index fell from 121.0 to 118.4, a decline of 2.1% over the course of 12 months.  This, however, was a better performance than the iGBGC Index of I-gaming companies which fell by 7.7% over the year from 269.1 to 248.5.GBGC Indices January Values