William Stanley Jevons (1835-1882)
English economist and logician
Jevons’ Sunspot Theory: From Curious Coincidence to Discredited Idea
In the late 19th century, the prominent British economist William Stanley Jevons proposed a fascinating, albeit unusual, explanation for the recurring boom-and-bust cycles of the economy: sunspots. This theory, linking celestial activity to earthly commercial crises, has a rich history, a controversial validity, and a unique modern legacy.
History: Connecting the Cosmos and Commerce
William Stanley Jevons was a pioneer of neoclassical economics, but he also possessed an insatiable curiosity for data and cycles. In papers read before the British Association in 1875 and 1878, he laid out his “sunspot theory”.
Jevons’ core argument was a chain of events:
- Variations in the number of sunspots (which follow an approximately 11-year cycle) affect the sun’s radiation and, consequently, the Earth’s weather patterns.
- These weather changes impact agricultural harvests (initially theorized for European corn crops, later for Indian harvests).
- Fluctuations in crop yields and prices influence business confidence, investment decisions, and overall aggregate demand, ultimately triggering commercial crises.
Jevons believed the near-10.5-year periodicity he observed in both sunspot activity and historical commercial crises was too “beautiful a coincidence” to be ignored, even as he changed the specific mechanism (e.g., from European harvests to Indian trade) several times.
Validity: A Flimsy Explanation
Despite Jevons’ careful, manual correlation of data, the sunspot theory faced significant scrutiny and was largely dismissed by the broader economics community during his lifetime and afterward.
The primary flaws and criticisms included:
- Irregular Cycles: Jevons assumed the solar cycle was highly regular (around 10.5 years), but in reality, its length and intensity vary considerably.
- Weak Link to Climate: Subsequent studies have found no strong or consistent link between the 11-year solar cycles and global climate fluctuations that would dramatically impact agriculture in the way Jevons posited.
- Shifting Economic Drivers: As economies became less agrarian over the 20th century, the influence of agricultural output on the overall business cycle diminished, further weakening the theory’s relevance.
- Lack of Statistical Significance: Later robust statistical analyses using modern data generally found only weak, statistically insignificant correlations between solar activity and economic indicators like GDP growth.
Current Status: A “Sunspot” by Name Only
Today, Jevons’ literal theory that actual sunspots directly cause business cycles is widely discredited in mainstream economics.
However, his work has an interesting modern legacy:
- “Sunspots” as an Economic Term: The term “sunspot” is now used in economic modeling (specifically “sunspot models”) to refer to any extrinsic, non-fundamental variable that, while having no intrinsic economic impact, can influence market participants’ beliefs and expectations, thus affecting economic activity.
- Influence on Behavioral Economics: John Maynard Keynes, while acknowledging the theory was flawed, agreed with Jevons’ underlying idea that market participants’ “moods” and psychological factors (what Keynes called “animal spirits”) play a role in driving business cycles. Jevons’ focus on expectations is seen as an early precursor to modern behavioral economics.
- Niche Research: Some recent, non-mainstream research has revisited the link, finding some weak correlations or suggesting a higher probability of recessions around solar maximums, but these findings remain highly controversial and are not widely accepted by the mainstream economic thought.
While Jevons was ultimately incorrect about the direct causal link, his pioneering use of data and his recognition of psychological factors in economic fluctuations have secured him a lasting, if indirect, place in economic history.
