Taxonomies for Transactions and User Engagement in Mobile Games

Mobile game monetization has grown into a market exceeding $150 billion as of 2019, yet the field lacks standardized vocabulary for describing how players and companies exchange value. This study addresses that gap by developing two taxonomies: one classifying transaction types, distinguishing direct monetization such as purchases, subscriptions, and gambling-like mechanisms from indirect monetization such as advertising and player acquisition, and another classifying engagement and retention elements, including log-in rewards, notifications, special events, and leaderboards. Both were built inductively from data gathered by 22 students who played 65 popular Android and iOS games over roughly a month, then refined against 20 additional titles.

The central argument is that shared terminology is a precondition for meaningful discussion among scholars, policymakers, and families about how monetization strategies and engagement mechanisms interact to sustain retention and potentially encourage addictive play. Prior literature has applied inconsistent labels to concepts such as soft currency and time skips, and the authors situate their work within existing research on microtransactions, loot boxes as gambling-adjacent mechanics, and psychological frameworks like appeal factors and variable-ratio reinforcement.

The paper's principal contribution is the transaction value map, an adaptation of value stream mapping that traces how real-world currency converts into in-game currency, boosts, and content. Illustrated with the game A Girl Adrift, these maps expose non-linear value conversions and locked content that players and stakeholders may otherwise overlook. The authors acknowledge that no existing quantitative or qualitative method measures net in-game value per transaction, and they position the taxonomies as the foundation for future work on cost-effectiveness and on disclosing randomized reward probabilities such as loot box odds.