The top 1 percent of monetizers account for 32.68 percent of money spent in "non-arcade" mobile games, according to a report from Playnomics (PDF link).
The company's analysis defines "non-arcade" games as those "designed and intended for longer term play experiences often featuring levels, campaigns and collectables." Playnomics studied more than 1.7 million players, observing spending patters over a three-month period. According to the report, the spending habits represent a "power law distribution," similar to the "whales" who spend disproportionate amounts of money over time in casinos. Playnomics expects 20 percent of monetizers to account for 80 percent of revenue.
Playnomics seeks to find out how and why people play games, and you can learn more about the company by reading our interview with Playnomics CEO and co-founder Chethan Ramachandran.