Tensions in Practice: A common offer can change the pool it was priced for¶

A toy two-member repair fund

Two members privately know different expected repair costs: Low expects 1 unit and will pay at most 2; High expects 5 and will pay at most 6. The fund cannot identify their types, but starts with the equal two-type mix and a common fee of 3. Compare optional participation with a prior collective rule requiring both members to pay. No action changes after joining: this is selection of types, not reduced care.

Preserve individual participation choice

Let each person refuse a common offer that does not suit their private situation.

Retain a mixed pool

Keep the low- and high-cost types in the same cost-sharing arrangement.

Why these aims pull against each other

The original fee reflects a two-member average. If the low type declines, that average no longer describes the members who remain. Keeping both in the pool avoids this selection change by imposing a transfer and limiting individual refusal.

Compare the arrangements

Allow refusal

At fee 3, Low declines and High accepts. With only High remaining, the stipulated expected-cost-covering fee becomes 5, still below High’s maximum 6.

What it protects: Each type can refuse the offer; no low type is made to pay above their stated willingness.
What it costs: The pooled fee 3 cannot cover the remaining expected cost 5. Selection has changed both membership and the common cost basis.
When it fits: Plausible when participation choice is central and the smaller high-cost-only pool is acceptable under the declared willingness assumptions.

Illustration note: This is an editorial, deliberately bounded illustration. Its stated rules and any numbers are invented, not observations, recommended settings, or predictions.

Keep both enrolled

A stipulated prior collective rule requires both fixed members to contribute 3 for the term. Each is entitled to repair coverage.

What it protects: Preserves the original average: total expected costs 6 are funded by two contributions of 3.
What it costs: Low pays 2 above their expected cost and 1 above their stated maximum willingness; individual refusal is constrained.
When it fits: Plausible only where a legitimate collective arrangement can bind the fixed membership for the term and members accept its distributional implications; no real legal authority is assumed.

Illustration note: This is an editorial, deliberately bounded illustration. Its stated rules and any numbers are invented, not observations, recommended settings, or predictions.

What this illustration does—and does not—establish

The source establishes the structural tension; the concrete alternatives and their conditional costs are editorial synthesis. No arrangement is a universal recommendation.

All expected costs, maximum payments and participation rules are invented. The example shows one selection step, not inevitable collapse, a full equilibrium, insurance pricing advice, or actual policy effects.
The required arrangement assumes fixed membership and enforceable prior authority for one term. If members can leave the underlying group, selection can reappear at that boundary.

Source entries

Adverse Selection

Prime · Source of the tension

Adverse selection T 2 supplies the local tension. The setting, alternative arrangements, and stipulated consequences are editorial applications.

Mandates Solve Selection but Create Transfers and Incidence

Mandatory participation (universal insurance, required licenses) prevents unraveling, but imposes cross-subsidies from low-cost to high-cost types.

Read the source section

Terms change pool membership

(2) The pooling mechanism — a single price or premium applied across types, under which types with higher-than-average costs to the uninformed side are more willing to transact than types with lower-than-average costs, inducing self-selection of the worst pool composition.