“…The past several decades have witnessed extensive development on optimal reinsurance design from different perspectives; see for example Borch [5,6], Arrow [3], Raviv [35], Young [40], Kaluszka [27], Cai et al [9], Cheung [12], Cui et al [18], Cheung et al [13,14], and the references therein. Under the assumption that both the insurer and reinsurer are obligated to pay more when the underlying claim is getting larger, 1 Chi and Tan [16] proved that the layer reinsurance contract is quite robust in the sense that it is always optimal over both value-at-risk (VaR) and tail value-at-risk (TVaR) measures under general premium principles including Wang's and Dutch premium principles as special cases. Recently, under the setting that all insurers use VaR or range value-at-risk (RVaR) measures, Bäuerle and Glauner [4] considered the optimal reinsurance problem from a macroeconomic point of view when there are 𝑛 insurance companies each bearing a certain risk and one representative reinsurer, and showed the optimality of the layer reinsurance treaty under certain conditions.…”