Fisher Separation Theorem
Updated 2026-08-05
INTRODUCTION
English translation pending.
CORE DEFINITION
The Fisher separation theorem states that in a perfect capital market, a firm's investment decision, whether a project is worth funding, can be separated from the owner's consumption preferences. Any project with a positive net present value should be accepted; the firm can borrow the funds, and owners can borrow or lend to arrange their preferred consumption. The key condition is a frictionless market with free access to credit; where borrowing is constrained, the separation fails.
SCAFFOLDING EFFECT
Reduce cognitive load
- Decision decoupling: judge a project by its net present value, not by the owner's current cash needs. - Role clarity: let business logic govern the firm while the shareholder's wallet answers to the market. - Friction test: confirm the capital market is close enough to perfect before applying it.
Anchor fast decisions
In a complete capital market, the firm maximizes present value by accepting every positive-NPV project, and owners then adjust their consumption by borrowing or lending. Since the market bridges the two, the investment and financing decisions are independent, and shareholder preferences do not change what the firm should invest in.
MINIMUM ACTION
In progress 0/1Practice this model in one real situation:
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Source support: Explicit
- en.wikipedia.orghttps://en.wikipedia.org/wiki/Fisher_separation_theoremverified
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