Gresham's Law: Bad Money Drives Out Good
Thomas Gresham, financial adviser to the English Crown in the sixteenth century, observed something that rulers had understood for millennia but economists had not yet formalized: when two currencies circulate at the same official exchange rate but differ in actual value, people hoard the good one and spend the bad one. Bad money drives out good.
The mechanism is simple. If the state declares that a gold coin and a debased silver coin are both worth one pound, rational people will spend the silver coin and keep the gold. Over time, the market fills with debased coins and the valuable ones disappear into hoards or cross borders to places where their intrinsic value is recognized. The official exchange rate collapses the information that would otherwise sort the currencies.
Why it generalizes beyond money
Gresham's Law appears wherever a fixed exchange rate prevents price from sorting quality. The canonical modern version: used car markets. George Akerlof's "lemons" paper showed that when buyers can't distinguish good used cars from bad ones, they offer an average price. Sellers of good cars, knowing their car is worth more, withdraw from the market. The average quality of cars offered for sale declines, buyers revise their maximum price down, more good-car sellers exit — until the market collapses or reaches a lemons equilibrium.
The pattern: a fixed rate (the average market price), two qualities of the same nominal good, and asymmetric information. The result is always the same: bad drives out good because the good has better alternatives.
In organizations: meetings, hiring, and the currency of attention
A meeting scheduled for one hour runs for two hours and accomplishes half what it promised. Bad time management drives out good: people learn the meeting will run long regardless, stop preparing, and arrive expecting the standard low-quality interaction. The meeting norms have set an exchange rate — one hour of nominal time equals one hour of actual time — that doesn't reflect reality.
Hiring shows the same dynamic. When a company signals that it doesn't distinguish rigorously between mediocre and excellent candidates — long waits, identical offers, opaque processes — the best candidates withdraw first. They have more options. The pool self-selects toward the people who have fewer alternatives.
In attention markets, low-quality content that is cheap to produce drives out the high-quality content that requires effort. If both rank equally in a feed algorithm, the incentive is to flood the zone with quantity. The exchange rate is impressions, and impressions don't distinguish effort.
India's informal credit market
India's informal lending markets illustrate Gresham's Law in a form that affects millions. Formal banks — the "good" currency of credit, with lower rates and longer tenors — serve borrowers with documentation, collateral, and credit history. Borrowers without these assets are directed to moneylenders at 36–60 percent annual interest — the "bad" currency.
The formal sector doesn't expand to absorb the informal one because the information problem isn't solved — the bank can't distinguish creditworthy informal-sector borrowers from risky ones at acceptable verification cost. So bad credit drives out good: informal credit proliferates while the formal market doesn't penetrate.
Jan Dhan, UPI transaction histories, and GST filings are all attempts to break this dynamic by creating information that allows formal credit to price informal-sector risk accurately. The solution to a Gresham dynamic is always the same: restore the information that the fixed exchange rate suppresses.
The diagnostic
Whenever a market or organization looks like it is being flooded with a low-quality version of something valuable, ask: is there a fixed exchange rate suppressing the price signal? Who is it that has alternatives — the good or the bad — and which way are they flowing? Gresham's dynamic is running when the answer is: the good are leaving, and the bad are filling the space they vacate.
Quick answers
What is Gresham's Law?
When two currencies circulate together, people hoard the more valuable one and spend the debased one. Sir Thomas Gresham's 16th-century observation applies far beyond currency.
