What it means
The original sunspot theory was put forward in the 1870s by the English economist William Stanley Jevons. He noticed that commercial crises appeared to follow a cycle of roughly a decade, similar to the cycle of dark patches on the sun, and argued that the sun affected harvests and therefore trade.
The evidence did not hold up, and the idea became a curiosity in the history of economics, though it gave later economists a memorable name for a serious question. Modern economists later gave the word a new meaning.
In a sunspot model, an irrelevant event, which could literally be sunspots or any random signal, can move the economy if everyone believes that it will. If enough people expect prices to rise and act accordingly, prices do rise, even though nothing real has changed.
The practical lesson for managers and investors is that expectations can matter as much as fundamentals. A rumour that a bank is in trouble can lead depositors to withdraw their money, which creates the trouble they feared.
A belief that a stock will fall can lead to selling that causes the fall. Such models are used to think about bank runs, asset bubbles and sudden changes in confidence.
They suggest that economies can sometimes settle into several different stable outcomes, and that a jump between them can be triggered by a small and arbitrary event. This explains why policymakers spend so much effort on communication and confidence.
The nuance is that the theory is an explanation of how things could happen, and it is hard to test. It does not tell a manager when a swing will occur, and critics say that it can excuse a lack of real explanation for events.
Even so, it is a useful reminder that markets are made of people, and that shared beliefs have financial consequences.
In practice
Real-world examples.
Example
A rumour spreads online that a regional lender is short of cash. Customers queue to withdraw $15 million in one morning, and the bank, which was healthy, has to borrow from the central bank to meet the demand.
Example
A group of retail traders become convinced that a small technology stock will rise, and buying by this group lifts the price by 40% in a week. Nothing in the firm's earnings changed, but the belief has made itself true for a time. When the buying stops, the price falls back, because the shared story was all that was holding it up.
Example
A commodity trader notices that a certain weather forecast is widely followed, though it has little link to actual supply. The trader prices in the market's reaction to the forecast rather than its accuracy, because behaviour is what moves the price. The trader also sets a stop-loss limit, since the same belief can fade as quickly as it formed.
Case study
Seen in the real world.
Coastline Savings Cooperative is an illustrative, fictional credit union with $400 million in deposits and a strong capital position. One week, a false message claiming that it had made large losses circulated among members.
Withdrawals rose from a typical $2 million a day to $18 million a day, and the finance director realised that the fundamentals had not changed but the belief had. She arranged an emergency credit line and published a short, clear statement of the cooperative's capital and liquidity.
Within four days the withdrawals fell back to normal. In this illustrative story, the lesson for the board was that confidence is a financial resource, and that a plan for communicating during a scare is as important as the balance sheet itself. The board approved a standing protocol naming who speaks to members, to the press and to the regulator when a rumour appears.
Watch out
Common mistakes.
- Thinking the sunspot theory is only about the sun, when modern versions use the word for any random signal that coordinates beliefs.
- Assuming that a belief-driven swing must be irrational, when each person may be acting sensibly given what they expect others to do.
- Using the theory to predict the timing of a crisis, when it only explains how such events could happen.
Questions
People also ask.
Who proposed the original sunspot theory of the business cycle?
William Stanley Jevons, a nineteenth-century English economist, proposed that solar cycles affected harvests and therefore the wider economy.
Why is it relevant to modern finance?
It helps explain bank runs, bubbles and sudden confidence shifts, in which beliefs move markets without any change in the underlying facts.
Can managers do anything about belief-driven swings?
Yes, they can keep clear communication, strong liquidity buffers and credible plans, which make it less likely that a rumour becomes a crisis.
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