Many companies at GAMA hold presentations. Most of them tell industry peers about upcoming plans and about sales and other figures for the last year. Fantasy Flight Games is no exception, and they showed a graph of some phenomenal recent growth, no doubt partly buoyed by great licenses including Star Wars, and boardgames for properties like Battlestar Galactica, World of Warcraft, Game of Thrones, and - of course, Warhammer RPGs of various flavours. The graph only goes up to 2014, though is cites 65% US growth and 35% growth outside the US, with really steep growth appearing to kick in somewhere around 2010.
(Photo from @WatchItPlayed)