Task: Question Generation
Input (English): Passage: According to the market research firm SuperData, as of May 2015, the global games market was worth USD 74.2 billion. By region, North America accounted for $23.6 billion, Asia for $23.1 billion, Europe for $22.1 billion and South America for $4.5 billion. By market segment, mobile games were worth $22.3 billion, retail games 19.7 billion, free-to-play Massively multiplayer online game 8.7 billion, social games $7.9 billion, PC Downloadable content 7.5 billion, and other categories $3 billion or less each.
Output (English): How many more billion were mobile games worth compared to retail games?