Thread: Where/How to find out how much an industry makes anually?

On the show shark tank, I see a lot of people pitching their product say that the (ex. granola bar business) is a $13 billion a year industry, how do they come up with that statistic? I am researching some different industries and would like to find out how much each one makes annually? Anyone know how I would go about that, i tried Google-ing it but no luck at all Also, please correct me on my vocabulary if im wrong

forresters research