# 搭便车问题与集体行动

> 【EN】In many contexts, the efficient production of a good by a group is jeopardized by the incentive each member of the group has not to contribute towards its production. If the benefit received by each member of the group depends mainly on the level of others’ contribution towards producing it, the cost of any one member’s contribution is likely to be greater than the resulting benefit to that member, and one member’s decision whether or not to contribute will have little effect on the level of contribution by others, then each member may have an incentive not to contribute, leaving the work of producing the good to the others. In situations with this structure, I can reason: if others are producing the good, I will receive it without contributing; if not, I will not receive it if I do contribute; so either way, I am better off not contributing. … 【中】词条先说明集体行动问题的结构，回顾从柏拉图、霍布斯、休谟到二十世纪的发展，再分析搭便车问题的成因——战略结构与心理因素——并把公共物品作为核心案例，讨论为什么理性的个体会共同导致谁都不想要的结果。

- ID: m13213
- 分类: culture
- 领域: 政治学

## 定义

搭便车问题指：群体高效地生产某种善，会因每个成员都有不贡献的激励而受到威胁。若每人所得主要取决于他人的贡献水平，个人贡献的成本高于其所得收益，且一人是否贡献对他人影响甚微，则人人都会倾向把生产留给别人。 脚手架作用：- 识别激励结构：检查成本自担而收益共享的安排，预判合作会在哪一环崩塌。 - 设计供给机制：用选择性激励、重复互动或可监督性，抵消搭便车者的占优地位。

## 机制

收益由群体共享而成本由个人承担，个体贡献的边际收益被摊薄，于是“不贡献”成为占优策略；当所有人都这样推理，公共物品就供给不足。这正是囚徒困境式的结构：个人理性与集体最优系统性地分离。

## 练习

1) 确认是否存在共享收益与个体成本；2) 估算个人贡献的边际收益与他人反应的弹性；3) 判断你的行为是否会影响他人的贡献；4) 引入选择性激励、制度约束或重复互动；5) 检验搭便车的空间是否被真正压缩。

## 脚手架用法

- 识别激励结构：检查成本自担而收益共享的安排，预判合作会在哪一环崩塌。 - 设计供给机制：用选择性激励、重复互动或可监督性，抵消搭便车者的占优地位。

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