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First-price sealed-bid auction

A painting is sold by sealed bid. You know what it is worth to you, somewhere between 0 and 100. The other bidder knows their own value, and neither of you knows the other's.

Both write down a bid. The higher bid wins and pays what it bid, so winning is worth your value minus your bid.

You are Bidder 1

What it teaches

When you pay what you bid you must shade below your value, and the right bid is simply what you expect the strongest rival to be worth in exactly those cases where your bid wins.

The usual mistakeBidding your value on the grounds that it is what the item is worth to you, which is correct advice for a second-price auction and leaves you with exactly zero surplus here.
The checkAsk what you earn in the event that you win. If it is nothing, the bid is too high regardless of how accurate your valuation is.

In the real world

Real world

A lowest-price public tender

Public bodies invite sealed tenders by a deadline and award to the lowest compliant price, and the winner is then held to the price it tendered. The recurring pattern is a winning price that turns out to be too low to deliver on, followed by claims, variations or an abandoned contract, which is what you would expect from a format that rewards whoever shaded hardest against their own costs.

It is the first-price auction with the signs reversed: the winner is paid its own number rather than the runner-up's, so the bid has to be built on beliefs about rivals, and shading is towards cost from above rather than towards value from below.

Real world

Offers over, by the closing date

Scottish residential sales are commonly run as offers over an advertised figure with a closing date. Each interested buyer submits a single written offer through a solicitor, the offers are considered together, and the seller normally accepts the highest, which that buyer then pays in full. Nobody sees anyone else's number, which is why the familiar outcomes are either paying well over the asking price or losing the house by a margin the buyer would gladly have covered.

The winner is held to the figure they wrote down, so the right offer depends on a judgement about how many rivals there are and what they are likely to put in, which is exactly the judgement a second-price rule would make unnecessary.

Real worldContested

Carillion winning work at any price

Carillion went into compulsory liquidation on 15 January 2018 with liabilities reported in the billions against a very small cash balance, having taken on large fixed-price public contracts at prices that could not cover the work. Its chief executive told MPs that with no money to buy competitors the company 'had to win our work organically'. Parliamentary committees blamed 'recklessness, hubris and greed' at the company, and separately criticised the practice of awarding public contracts on lowest price. Inference, not fact: the revealed preference looks like bidding to win cash flow rather than bidding to make a margin, which is a rational response to needing the next contract to fund the last one, and is precisely the shading error a pay-your-bid format punishes last and hardest.

The winner is held to the number it wrote down, so the optimal bid depends on a judgement about rivals rather than on your own costs alone, and a bidder who shades too far wins exactly the contracts it should have lost; under a second-price rule the winner would be paid the runner-up's price and the error would not be self-inflicted in the same way.

Next door on the wall

Ideas in this game

Sources