💰 Value, Supply, and Demand: A Diamond-Water paradox

⚖️ Setting the Stage

We explored Mill’s take on business cycles—how economies rise and fall. Now, we zoom in on the heartbeat of the marketplace itself: value.

For Mill, understanding value wasn’t just about numbers; it was about human behavior, scarcity, and utility—ideas that still power modern economics.

🧩 What Is “Value,” Anyway?

Mill distinguishes between two forms of value:

1. Value in Use – The usefulness of a thing (like water or food).

2. Value in Exchange – What it can be traded for in the market (like gold or land).

Here’s Mill’s insight:

Something can have immense use value but little exchange value—like air. And something can have high exchange value but limited use value—like diamonds.

Sound familiar? That’s the “diamond-water paradox” first raised by Adam Smith, which Mill expands on beautifully.

🧮 The Three Pillars of Price Formation

Mill’s theory of market price rests on three foundational forces:

1. Demand

The total desire to acquire a good, backed by the ability to pay. He was clear: desire alone doesn’t count; it must be effective demand.

2. Supply

The total quantity of a good available for sale at various prices. Producers adjust supply based on profit expectations and production costs.

3. Cost of Production

Unlike pure demand-supply models, Mill adds the real-world constraint—the cost of making things. Labor, capital, and time form the backbone of value in the long run.

🌀 Market Price vs. Natural Price

Mill distinguishes between market price (the here-and-now price) and natural price (the long-term equilibrium).

• Market Price fluctuates with temporary changes in demand or supply—think of seasonal goods or sudden shortages.

• Natural Price gravitates around the cost of production, acting as a kind of “economic centre of gravity.”

Over time, competition pulls prices toward their natural level.

“The value of a thing... ultimately depends on the cost of production.” — J.S. Mill

📈 When Demand and Supply Dance

Mill’s model beautifully captures the dynamic balance between producers and consumers:

• If demand rises and supply is constant → prices go up → more producers enter → supply expands → prices fall again.

• If demand falls → prices drop → producers cut back → supply shrinks → equilibrium returns.

This rhythmic interplay is the invisible hand of adjustment.

💡 A Modern Lens

Mill’s ideas still echo in modern economics:

• His “natural price” mirrors today’s long-run equilibrium price.

• His view of demand anticipates elasticity theory.

• His balance between utility and production costs forms a bridge between classical and neoclassical economics.

Essentially, Mill was standing at the crossroads—looking back to Adam Smith and forward to Alfred Marshall.

🧭 Takeaways

• Value has two faces: usefulness and exchangeability.

• Prices are shaped by the triad: demand, supply, and cost.

• Market prices swing, but natural prices stabilize the system.

• Mill helped build the transition from moral philosophy to modern market science.