public good

A public good has two properties that make it different from normal Capital Investments:

1. 1)One party using it doesn't reduce its value for others. If Company A uses the shared compliance platform, Company B still gets the full benefit. Compare this to inventory - if you sell a unit, it's gone.

2. 2)You can't practically stop non-payers from benefiting. If the platform exists, everyone in the portfolio can use it whether they paid or not. Compare this to a Subscription Pricing product where you can revoke access.

The combination is what makes funding break down. Any single good that's easy to share and hard to restrict access to is a public good - industry standards, shared threat intelligence, common data infrastructure, even a clean break room.

The node description frames this as countries forming coalitions, but the mechanics are identical when business units, PE portfolio companies, or vendors need to jointly fund something that benefits everyone.

Public goods show up constantly in Operations and they quietly destroy value when mishandled:

• •Shared infrastructure across a portfolio. A Holding Company with multiple brands needs shared data pipelines, security tooling, or compliance platforms. Each brand's P&L wants to minimize its own overhead, so no one volunteers to fund shared services.

• •Industry consortium investments. Competing retailers funding a shared fraud detection network. Everyone benefits from the data, but each firm's CFO sees it as a Cost Center on their Operating Statement.

• •Internal platform teams. Your engineering org builds shared tooling. Every product team benefits, but none want the Cost Per Unit hitting their Budget. The platform team is a public good - and it's chronically underfunded for exactly this reason.

The P&L impact is indirect but large. When public goods go unfunded, each team builds their own inferior version. You pay 5x the Implementation Cost across the portfolio for 0.5x the quality. The surplus that a shared investment would create simply evaporates.

The Core Tension

Consider three business units that would each get $500K/year in value from a shared analytics platform costing $600K to build.

• •Collective ROI: $1.5M value on $600K spend. Obvious win.
• •Individual logic: If the other two fund it, I get $500K in value for free. If I'm the only one paying, I spend $600K for $500K in value - a loss. My Dominant Strategy is to wait.
• •Result: Nobody funds it. $900K in annual surplus ($1.5M - $600K) never materializes.

This is the public good trap. Individual rationality produces collective stupidity. Game Theory predicts this: when your Outside Option is 'benefit without paying,' contributing is never your best move unless the structure forces it.

The Externality Connection

When one company builds the platform, it generates a positive Externality - value that spills over to others who didn't pay. The Externality framework from your prerequisites tells you to measure this: what does each party's participation add to (or subtract from) others' outcomes? That measurement is the foundation for fair cost sharing.

Coalition Formation

Solving public goods means building a consortium where enough parties commit to make the investment viable. Three mechanisms work:

1. 1)Central authority funds it. The Holding Company or CFO mandates the investment and allocates cost across business units. No negotiation needed, but you need the authority.

2. 2)Shapley value cost sharing. Compute each party's marginal contribution to the coalition's value across every possible grouping. This gives a fair split that makes every participant better off than their Outside Option of going alone. Turns the political argument into arithmetic - exactly what your cost sharing prerequisite teaches.

3. 3)Binding agreements with committed funding. Parties sign contracts specifying their share before the good is built, removing the option to wait and benefit for free. The commitment solves the timing problem.

Why Voluntary Funding Fails

Imagine each party privately decides how much to contribute. Each party's Utility Maximization says: contribute the minimum possible, because every dollar someone else contributes gives me the same benefit. The equilibrium of voluntary contributions is always below the Efficient Allocation. This isn't a behavioral flaw - it's the mathematically predicted outcome when rational actors face a public good.

Recognize a public good situation when all three conditions hold:

1. 1)Multiple parties benefit from the same investment. If only one business unit needs it, it's just a normal Capital Investment decision.

2. 2)Beneficiaries can't be excluded from using it. If you can gate access (like a Subscription Pricing product), charge for it directly. No public good problem.

3. 3)One party's usage doesn't diminish another's. If the resource has capacity constraints (like a shared analyst's time), it's a common resource, not a public good. Different problem, different solution.

When all three hold, don't rely on voluntary funding. Choose your mechanism:

• •You have authority (you're the Holding Company, you own the P&L): mandate the investment and allocate cost using Shapley value or proportional benefit.
• •You're a peer in the coalition (equal-rank business units, companies in a consortium): negotiate binding agreements with a cost sharing formula before building.
• •You're the builder with no authority: frame the proposal as each party's Outside Option cost. 'You can build your own for $600K, or join the shared build for $200K.' Make the math impossible to ignore.

Public goods sit at the intersection of your three prerequisites. Game Theory explains why rational actors underfund them - when your Dominant Strategy is to let others pay, collective action fails without enforcement. Externality pricing measures the spillover value each participant creates for others, which is the foundation for deciding who should pay what. And cost sharing via the Shapley value provides the arithmetic to allocate costs fairly once you've formed the coalition. Downstream, public goods connect to Efficient Allocation - the operator's job is ensuring that shared investments actually get made when their collective ROI justifies them, rather than letting individual P&L optimization kill projects that create massive surplus. The concept also feeds into overhead management and consortium strategy in PE portfolio companies, where the Holding Company must decide which investments to centralize (fund as public goods) versus which to leave to individual brands.