When Should Control Be Shared?: with limits on transfers, a better-informed stakeholder raises the surplus of shared control and leaves that of undivided control unchangedResearch Paper
Motivation
Corporate law and contract design decide who controls a firm's decisions. A manager may hold undivided control, the unfettered right to implement a project, or control may be shared, with a stakeholder (a creditor, an employee group, a minority shareholder) holding a contractual veto. The trade-off is old: veto rights protect stakeholders from value-destroying decisions, but they create a bargaining problem when the stakeholder is less informed than the manager, because negotiations under asymmetric information can break down and block valuable projects.
E. M. Meyersson Milgrom, P. Milgrom and R. Singh, When Should Control Be Shared? (Management Science, 2023, doi:10.1287/mnsc.2022.4356), study this trade-off in a two-party model and add a legal dimension: rules that forbid extortionate transfers (duties of loyalty, good faith and fair dealing). Their headline comparative static is that, once such limits on transfers accompany undivided control, a better-informed stakeholder helps only the shared-control structure. Shared control is then more attractive the more symmetrically informed the parties are, which is the opposite of what happens without the legal limits (their Proposition 3).
Setting
A firm has a manager, who generates a proposal, and a stakeholder. With probability the state is good, otherwise bad. The project moves a random amount of wealth from the stakeholder to the manager; in state the payoffs are
The redistribution has a continuous distribution with support , , and mean . The manager observes ; the stakeholder observes it only with probability .
The manager makes a take-it-or-leave-it offer of a transfer . Under shared control, an uninformed stakeholder facing an offer that is made exactly when accepts if
and the equilibrium transfer is the smallest nonnegative satisfying (1). With , the joint expected surplus of shared control is
Under undivided control with transfers disallowed, the manager implements a proposal whenever , and the joint expected surplus is
Formalization targets
Goal: Proposition 8
For every model satisfying the standing assumptions,
The paper's "corresponding increase in the benefit of shared control" is read as weak monotonicity together with the exact condition for strictness: when good proposals are never blocked (), is constant in .
Milestones
- The equilibrium transfer exists (§2.1): the infimum of the transfers satisfying (1) satisfies (1), and either or (1) holds with equality at .
- Full acceptance (proof of Proposition 1): for every threshold .
- The threshold (proof of Proposition 1): .
- Proposition 1: under shared control no transfer makes a bad proposal profitable for the manager and acceptable to the stakeholder, and .
Significance
Proposition 8 is the result behind the paper's abstract claim that with legal protections against extortion, "but not without them", shared control is more likely when the parties are more symmetrically informed. It turns the informational environment into a determinant of the optimal control structure: improving the stakeholder's information (disclosure duties, audit rights, board observers) raises the value of a veto right and leaves undivided control unaffected. Proposition 1, the main intermediate step, gives the exact condition under which shared control loses nothing to bargaining failure.
The results are proved in the paper, in prose. Nothing of this model is formalized. A machine-checked version adds an explicit account of the equilibrium transfer, which the paper defines as "the smallest nonnegative transfer that satisfies Inequality (1)" without proving that the set has a least element, and it fixes the exact sense in which the increase in Proposition 8 holds: weak in general, strict exactly when and .
Difficulty
Once Proposition 1 is available, the goal is close to algebra: is affine in with slope , and does not involve . The work lies in the equilibrium transfer. The left-hand side of (1) is a conditional expectation over an event that moves with , so continuity in needs the atomlessness of the law of , and attainment of the infimum needs the conditioning event to keep positive probability up to . The strictness criterion then needs both directions of Proposition 1, and the "only if" direction uses that is the minimum of the support, not just a lower bound: below there must be probability mass for the good proposal to be blocked.
Formalization scope
The model is a structure SharedControl.Model (probability measure P on Ω, redistribution r : Ω → ℝ, parameters πg, πb, q, rl, rh) with a separate predicate SharedControl.Standing: P a probability measure, r measurable, the law of r atomless (NullSingletonClass), r ∈ [rl, rh] almost surely, rl and rh the essential infimum and supremum, , , , . No density is assumed. is the integral against Mathlib's conditional measure P[|A]; a transfer satisfies (1) only if , since the conditional measure of a null event is zero and would make every large transfer acceptable by a junk value. The equilibrium transfer ts is the sInf of the feasible set, and the goal is stated for this defined ts, not for a free variable with an IsLeast hypothesis. Probabilities are real numbers (P.real). S and Utilde are functions of , the latter ignoring its argument; monotonicity is on .
The statement is not trivialized: clause 3 holds by the definition of (7) because that is the paper's claim about undivided control, but clauses 1 and 2 depend on ts being a genuine least element and on both directions of Proposition 1.
A complete development needs continuity of conditional expectations over moving tail events for atomless laws, which is reusable beyond this mission. Proofs of the milestones in any order, and alternative arguments, are welcome.
Selected references
- E. M. Meyersson Milgrom, P. Milgrom, R. Singh, When Should Control Be Shared?, Management Science, 2023 (Articles in Advance, 2022). https://doi.org/10.1287/mnsc.2022.4356
- O. Hart, J. Moore, Property Rights and the Nature of the Firm, Journal of Political Economy 98(6), 1990. https://doi.org/10.1086/261729
- P. Aghion, P. Bolton, An Incomplete Contracts Approach to Financial Contracting, Review of Economic Studies 59(3), 1992. https://doi.org/10.2307/2297991