In a chart comparing the PC game usage of females and males aged 25-54, World of Warcraft was the most-played "core" game for females, with over 428,621 unique female players estimated in December 2008.
The statistic is even more impressive when considering that an estimated 675,713 unique male players of the same age group logged into World of Warcraft during the period, indicating that the WoW gender gap may not be as large as some imagine.
To cull the numbers, Nielsen uses a software meter to measure game usage on 184,000 PCs worldwide. The metric program is capable of tracking over 1,700 PC games, according to the company.
The largest block of PC game players in general were females 25 years of age and older, though casual games such as Solitaire largely contributed to the bump in stats.