The amount of information released about a video game before it is available to purchase varies quite a bit. Sometimes you just get a few screenshots, maybe a story and gameplay videos, too. Other times you also get a demo to play, but that demo can be held back for a few months until after the game has been released.New data from video game research and consulting company EEDAR suggests releasing a demo may be the worst thing a publisher can do, though. In fact, it may even halve sales of a title.That claim was made by game designer Jesse Schell who gave a keynote speech at the GameLab 2013 conference earlier this week. One of the slides he put up during his speech came from EEDAR and focused on Xbox 360 game sales (you can view it above).The slide suggests that not promoting a game at all will typically see sales stay below 100,000 units. Releasing just a demo means less than 200,000 sales, and releasing a demo and trailer sees sales of around 250,000 units. All of those figures are for the first 6 months a game is available.But the standout sales figure is when a game only has a trailer released. In that case a publisher can expect around double the sales, roughly 525,000 units. Of course, there’s going to be a lot of variation based on what that game is, whether it carries a well known name, and what the marketing campaign is like. But the slide suggests that this is an average and regardless of the game, publishers/developers are better off not wasting any time releasing a demo.It’s hard to draw any concrete conclusions from this because we don’t know what games were used to compile the data. It does raise a few questions for game makers, though. Demos are not free to produce, and typically require extra development time and a separate review process before they are made available. If a demo actually reduces sales for the majority of titles, then there really is no point spending the time making them.Of course, gamers will disagree as a demo is a great way to find out if you like a game or not before spending any money. An alternative to not doing a demo is actually creating a great demo that makes gamers want to place a pre-order.