Why a free shortcut can make everyone's commute longer: Braess's paradox
30seconds
Build a brand-new road and every commute gets longer. In a town of 4,000 drivers, two routes each take 65 minutes. Add a free shortcut and each driver, choosing the quickest route for themselves, piles onto the roads that jam, so everyone ends up at 80 minutes. Nobody can do better by switching alone, yet everyone loses.
Open and close the shortcut, slide its travel time, and watch the cars re-route. This is Braess's paradox, a classic of game theory.
Deep dive · 5 min
More in Economics
View all →
Why the auction winner so often overpays: the winner's curse
Why does the winner of an auction so often go home poorer? When a prize is worth the same to everyone, each bidder only has a noisy estimate, and winning means…
Why mild preferences can build a segregated town: Schelling's chequerboard
Nobody in this town wants it split into blue and orange districts. Each household only asks that a few of its neighbours look like it. Yet run the rule and the…
Why good used cars vanish from the market: Akerlof's lemons
Why can a market of willing buyers and sellers fall apart? In 1970 the economist George Akerlof showed that when only the seller knows a used car's quality…
Why rival ice-cream carts end up side by side: Hotelling's beach
Put two ice-cream carts on a long beach and each one is tempted to creep toward the other, because standing next to a rival steals customers without losing…
Why adding a road can slow every driver down: Braess's paradox
You would think a free shortcut can only help. In 1968 the mathematician Dietrich Braess showed it can make every driver slower. In our four-road example…
Why people bid more than a dollar for a dollar: Shubik's escalation trap
Auction a dollar bill with one twist: the second-highest bidder pays their bid too. It sounds harmless, yet in 1971 economist Martin Shubik reported that…