New data from games industry research and consultancy firm EEDAR suggests that releasing demos can actually have a detrimental effect on game sales.
Game developer Jesse Schell presented the data during a keynote speech at the Gamelab conference in Barcelona (via CVG).
Schell's slide showed that the average Xbox 360 game sells 525,000 units after six months when released with a trailer but no demo. On the contrary, a game with both a demo and a trailer will only sell about 250,000 units.
An average Xbox 360 game released without a trailer nor a demo sold fewer than 100,000 copies in the same time period, however.
One potential problem with interpreting the EEDAR data in this way, however, is that it is difficult to determine whether there is a correlation between some of the industry's best-selling titles--such as Call of Duty, BioShock Infinite, or Tomb Raider--generally opting not to release a demo at launch.