Incomplete contracts

No contract can foresee everything. The gaps that inevitably remain, and who fills them, shape much of economic life. That is the problem of incomplete contracts.

Incomplete contracts are agreements that cannot specify what is to happen in every possible future circumstance, leaving gaps that must be filled later as events unfold. Because the future is uncertain and complex, and writing fully detailed contracts is costly or impossible, virtually all real contracts are incomplete, and this incompleteness has profound consequences.

Why contracts cannot be complete

A complete contract would specify the obligations of each party in every conceivable situation. Reality defeats this: the future holds too many contingencies to foresee, many are too hard to describe precisely, and even where outcomes can be imagined, they may not be verifiable by a court, so a clause covering them could not be enforced. Add the sheer cost of negotiating and writing exhaustive terms, and complete contracts become impossible. Every real agreement therefore leaves gaps, silences about what happens if circumstances arise that the parties did not, or could not, anticipate.

The problem of the gaps

Incompleteness matters because it leaves room for dispute and for one party to exploit the other when an unforeseen situation arises. When a contract is silent, who decides? The party with more power, or with control over the relevant assets, can hold up the other, demanding better terms once they are committed and vulnerable. This risk of hold-up, especially where parties have made relationship-specific investments, shapes how they structure their dealings, sometimes deterring valuable investment that the fear of later exploitation makes too risky.

Why it explains so much

The theory of incomplete contracts, developed by Oliver Hart and others, explains a great deal about economic organisation. Because contracts cannot specify everything, ownership matters: whoever owns an asset holds the residual right to decide about it in situations the contract did not cover, which is why the allocation of ownership, the boundaries of the firm, vertical integration, is so consequential. Firms internalise activities partly to control the residual rights that incomplete contracts leave hanging, replacing fragile agreements with ownership and authority.

Incomplete contracts are a deep and unifying idea, the recognition that agreements can never cover every contingency, and that the resulting gaps shape investment, power, and the very structure of firms. They explain why ownership matters, why hold-up is a danger, and why so much of economic organisation is a response to the simple, inescapable fact that no contract can foresee everything.