Reuters has an article Health games become serious business drawing on the recently growth of serious games:

“Healthcare is 18 percent of the GDP of the United States and so games for health is probably the largest sector of activity in the serious games field long-term,” said Ben Sawyer, co-founder of The Games for Health Project.

“If you add up the 18 month sales of “Wii Fit” and the sales of “EA Sports Active,” Konami’s “Dance Dance Revolution” and other healthy games, the worldwide retail numbers are over $2 billion.”