  Real-world observed contests often take the form of multi-task contests
rather than single-task contests, and existing theories are insufficient to
explain the incentive for extending the task dimension. This paper proposes a
new effect of multi-task contests compared to single-tasking contests: the
specialization effect (SE). By establishing a multi-task contest model with
heterogeneous competitor costs, this paper shows that after expanding the new
competition dimension, competitors will choose the dimension with greater
relative comparative advantage rather than absolute advantage and pay more
effort, which eventually leads to competitors choosing higher effort levels in
both the original dimension and the extended dimension. The paper then uses
staggered Difference-in-Difference (DID) method on China's county officers'
promotion assessment from 2001 to 2022 as an entry point to discuss the
empirical evidence for specialization effect. Through models and empirical
studies, the specialization effect studied in this paper do exists in promotion
assessments, and may also explain many other real-world scenarios, such as
sports events, competition between corporate compensation and employee benefits
and competition for R&D expenses.
