Week 11: Mechanism Design and Game Theory Crossover

Auction theory shows up in every market this course has studied — this is the week we name it properly and ask what it would mean to design one on purpose.

10 May 2027

Every market this course has looked at is, underneath the UI, a kind of auction — and auction theory has a genuinely rigorous answer to a question game designers usually solve by feel: what rules make people bid what they actually think something is worth?

The core result, briefly#

In a first-price sealed-bid auction, the winner pays what they bid, so the rational move is to shade your bid below your true value — bid your real number and you win, but overpay. In a second-price (Vickrey) auction, the winner pays the second-highest bid, which removes the incentive to shade: bidding your true value is the dominant strategy, because the amount you actually pay no longer depends on your own number.

None of the three case-study markets run a literal second-price auction, but the idea — design the payment rule so honesty is the winning strategy — is exactly the lever a designer is pulling whenever they add a price band, a matching algorithm, or a delayed settlement to a market.

Where this connects back#

RuneScape’s price band (Week 3) and EVE’s fully transparent order book (Week 9) are both, in mechanism-design terms, attempts to make the truthful strategy also the winning one, just aimed at different failure modes: the band against cornering, the transparency against information asymmetry.

A concrete adoption#

Old School RuneScape’s Grand Exchange only runs one clearing rule — an open, continuous order book — for every trade regardless of size. It could instead route only its largest, one-off trades (a rare item worth hundreds of millions of gold, say) through a sealed-bid, second-price clearing option alongside the existing book: bidders on that specific item submit private bids once, the highest bidder wins, and pays the second-highest bid. That removes the incentive a big buyer currently has to shade a large order down for fear of moving the visible book against themselves. The tradeoff is real, though: the open book’s whole value for everyday small trades is that the price is visible and the fill is instant, and a sealed-bid round sacrifices both — bidders wait for the round to close, and nobody outside it can see what the item actually traded for until after the fact.

Studio’s over, but the question isn’t#

There’s no dedicated studio for this week — it feeds straight into the capstone. Start thinking now about which market, and which specific mechanism-design lever, your Economic Intervention Report will use.