尺度效应：群体规模会改变合作规则

家庭、社区、城市和国家都由人组成，却不能使用完全相同的合作规则。小群体可以依靠熟悉关系、声誉和重复互动维持合作。人一多，匿名性增加，谁搭过便车、谁欠过谁东西，很快就记不住了。

这与 邓巴数：信任的成本上限 相邻，但两者并不相同。邓巴数讨论一个人大致能够维持多少稳定关系；尺度效应讨论群体扩大以后，原来有效的治理方式为什么会失效。法律、层级和 想象的共同体 都是在熟人关系之外继续合作的办法。

塔勒布引用的那句话很准确：

I am, at the Fed level, libertarian; at the state level, Republican; at the local level, Democrat; and at the family and friends level, a socialist.

同一个人在家庭中分享资源，在地方层面支持公共服务，在国家层面又警惕权力扩张，未必是立场矛盾。不同尺度提供的信息和约束本来就不一样。

《Skin in the Game》原文：

Yaneer Bar-Yam showed quite convincingly that “better fences make better neighbors”—something both “policymakers” and local governments fail to get about the Near East. Scaling matters, I will keep repeating until I get hoarse. Putting Shiites, Christians, and Sunnis in one pot and asking them to sing “Kumbaya” around the campfire while holding hands in the name of unity and fraternity of mankind has failed. (Interventionistas aren’t yet aware that “should” is not a sufficiently empirically valid statement to “build nations.”) Blaming people for being “sectarian”—instead of making the best of such a natural tendency—is one of the stupidities of interventionistas.

But we don’t have to go very far to get the importance of scaling. You know instinctively that people get along better as neighbors than roommates.

There is no way you can get the same cohesion in a larger city when the “other” is a theoretical entity, and our behavior toward him or her is governed by some general ethical rule,

What Ostrom found empirically is that there exists a certain community size below which people act as collectivists, protecting the commons, as if the entire unit became rational. Such a commons cannot be too large. It is like a club. Groups behave differently at a different scale. This explains why the municipal is different from the national. It also explains how tribes operate: you are part of a specific group that is larger than the narrow you, but narrower than humanity in general. Critically, people share some things but not others within a specified group. And there is a protocol for dealing with the outside.

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