  Monetary markets serve as established resource allocation mechanisms,
typically achieving efficient solutions with limited information. However, they
are susceptible to market failures, particularly under the presence of public
goods, externalities, or inequality of economic power. Moreover, in many
resource allocating contexts, money faces social, ethical, and legal
constraints. Consequently, research increasingly explores artificial currencies
and non-monetary markets, with Karma emerging as a notable concept. Karma, a
non-tradeable, resource-inherent currency for prosumer resources, operates on
the principles of contribution and consumption of specific resources. It
embodies fairness, near incentive compatibility, Pareto-efficiency, robustness
to population heterogeneity, and can incentivize a reduction in resource
scarcity. The literature on Karma is scattered across disciplines, varies in
scope, and lacks of conceptual clarity and coherence. Thus, this study
undertakes a comprehensive review of the Karma mechanism, systematically
comparing its resource allocation applications and elucidating overlooked
mechanism design elements. Through a systematic mapping study, this review
situates Karma within its literature context, offers a structured design
parameter framework, and develops a road-map for future research directions.
