Because contracts are linked with each other, one default can trigger an avalanche of broken promises, “[making] it possible to destroy virtually the entire web of formal and informal contracts which the market system requires for its functioning.” The state’s role is to protect, enforce, and regulate these contracts and related property rights, as well as to intervene to prevent systemic failure.
发自香港——经济学家阿克塞尔·莱琼霍夫德（Axel Leijonhufvud）在近期的一篇文章中将市场体系定义为一个合约网络。由于合约之间彼此关联，一份合同的违约可能影响一系列承诺的兑现，如雪崩一般不断扩大，进而“破坏市场体系正常运转所需要的整个正式与非正式合约的网络系统”。国家的作用正是保护、强制执行并规范这些合约以及相关的财产权利，并适时干预以防系统性失灵。