How big is the type design industry?

I'm not sure if this has been discussed in the past (at least I couldn't find anything on this topic), I was wondering if somebody knows the estimated value of the type design industry? How big is it really? Based on a current report, the global Graphic Design industry generates a whooping $56 Billion in a year. Considering fonts are also part of the Graphic Design industry, what would be the estimated worth of type industry? $5 Billion? $10 Billion? 20 Billion?

Any information would be useful.