also led to the creation of the "AA" market in the industry, larger studios that were not at the scale of AAA developers but had more experience, funding, and other factors to make them distinct from the smaller teams usually associated with indie studios. AAA game development has been identified as one environment where crunch time and other working pressures that negatively affect employees are particularly evident. Related terms AAA+ In general use, the term "AAA+" (Triple-A-Plus) may refer to a subset of AAA games that are the highest selling or have the highest production values. However, there are at least two more specific meanings. The first describes AAA games with additional methods of revenue generation, generally through purchases in addition to the cost of the base game. The desire for profitability has caused publishers to look at alternative revenue models, where players continued to contribute revenue after the initial purchase, either by premium models, DLC, online passes, and other forms of subscription. In the mid 2010s large publishers began a focus on games engineered to have a long tail in terms of revenue from individual consumers, similar to the way MMO games generate income – these included those with expansion or season pass content such as with Destiny, Battlefield, and the Call of Duty series; and those which generated revenue from selling in-game items, sometimes purely cosmetic, such as Overwatch or League of Legends. Titles of this type are sometimes referred to as "AAA+". In 2016, Gameindustry.biz described AAA+ games as products that "combine AAA production values and aesthetics with Software as a Service (SaaS) principles to keep players engaged for months or even years". AA (Double-A) "AA" or Double-A games are mid-market video games that typically have some type of professional development though typically outside of the large first-party studios of the major developers; these may be from larger teams of indie developers in addition to larger non-indie studios. Double-A studios tend to range from 50 to 100 people in size. A double-A development studio will typically be backed by a publisher but not fundamentally part of that publisher, and thus have somewhat more freedom to innovate and experiment compared to triple-A studios, though will still be constrained by specific risk-limiting targets and goals from their funding source. Double-A games tend to be priced compared to (as of 2021) that triple-A games are priced at. Examples of games