In an effort to stop developers from artificially inflating review scores on Steam, Valve has changed the system so that reviews written by users who received a game via a developer- or CD-distributed licence key will no longer count towards the review rating. The change will also affect reviews from Kickstarter backers that receive a Steam key as part of their backer rewards.

The Steam review system was updated in May so that an overall review rating (positive, negative, or mixed) is displayed at the top of each game page. The idea was to better show the current state of a game, particularly as more of them enter early access and evolve over time. Unfortunately, Valve claims that many developers have been abusing the system by giving out keys to friends or paid-for review services in order to bolster the overall review score.

"The review score has also become a point of fixation for many developers, to the point where some developers are willing to employ deceptive tactics to generate a more positive review score," wrote Valve in a blog post.

"The majority of review score manipulation we're seeing by developers is through the process of giving out Steam keys to their game, which are then used to generate positive reviews. Some developers organise their own system using Steam keys on alternate accounts. Some organisations even offer paid services to write positive reviews."

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Valve estimates that "at least 160 titles have a substantially greater percentage of positive reviews by users that activated the product with a CD key, compared to customers that purchased the game directly on Steam." While it admits there can be legitimate reasons for the discrepancy—including strong audiences outside of Steam and popular Kickstarter campaigns—for the most part it says "the abuse is clear and obvious."

Valve will not be removing the ability for developers to issue Steam keys. But in cases where it finds developers have duplicated or generated reviews in large batches, or found review accounts linked to the developer in question, it "will be ending business relationships." Gamers that purchase or receive a game outside of Steam will still be able to write a review, but it will no longer contribute to the overall review score.

"This does mean that the review score category shown for about 14 percent of games will change; some up and some down," continues Valve's blog post. "Most changes in the review score category are a result of games being on the edge of review score cut-offs such as 69 percent positive or 70 percent positive. A change of 1 percent in these cases can mean the difference between a review score category of 'Mixed' and 'Positive.' About 200 titles that only had one or two reviews will no longer have a score at all until a review is written by a customer that purchased that item via Steam."

While the change is largely positive for consumers, developers that have large fanbases outside of Steam or rely on crowdfunding could be negatively affected. Valve is also working on other issues that include a mismatch between the most helpful reviews and the review score, which can be caused users intentionally trying to skew the system, or where reviews are helpful "simply because they are funny."