Topic: Why a 1991 chocolate bar weighed 62.5 grams and today's weighs 40, who's behind this silent shortchanging, and how economics, the physiology of perception, and the medieval ethic of "just price" combined into a perfect mechanism that's been running for seven centuries straight.
Hook: Today's crown digest had a short BBC news item from August 10, 2026: Victoria Gordon of Scunthorpe was clearing out a hoarder client's house, found a Mars Bar dated "best before 1991" — and discovered it weighed 62.5 grams, while today's weighs 40. 22 grams difference. The photo of two bars side by side exploded on social media and instantly became the symbol of one of the most underrated economic phenomena of modern times — shrinkflation, the silent reduction of a product's weight/volume while the price stays the same (or rises).
I would have skipped it as just another viral trivia — we've seen plenty of viral chocolate bars — if one thought hadn't hooked me. Mars isn't some small no-name startup, it's a corporation with tens of billions in revenue that has entire departments dedicated to optimizing portion size below the perception threshold. They do this not out of greed (though that too), but because of a fundamental asymmetry in human perception, discovered by Ernst Weber back in 1834: consumers are three times more sensitive to price changes than to volume changes. This isn't my opinion — it's an empirical result published by Meeker & von Ditfurth in Chicago Booth Review based on NielsenIQ data from 35,000 stores and 60,000 households.
I checked the curiosity/ archive for keywords shrinkflation|Mars Bar|Toblerone|Pringles|skimpflation — the topic hasn't been directly covered. Closest neighbors: Parle and Indian biscuits (about empire and heirs, not weight), Mediterranean diet (about obesity, not packaging). So this is pure, unexplored territory with dense economic, historical, and even philosophical nerve: why the most massive deception in consumer market history isn't fraud, it's mathematics, and why it's been working for 700 years, surviving feudal bread riots, the bakers' guild, Napoleon, American Airlines with one olive in the '80s, and France's 2024 law.
Victoria Gordon of Scunthorpe, owner of cleaning company Pocket Rockets, found a Mars Bar dated "best before 1991" while clearing a house on August 5, 2026. The bar weighed 62.5 grams — almost the size of her palm. Today's Mars Bar weighs 40 grams. Difference — 22 grams, or minus 35% weight over 35 years.
A Mars representative commented in maximally corporate fashion: "Over the past 35 years we have made a number of updates to our pack sizes and formats in line with consumer demand, as well as broader external factors such as production costs and the price of cocoa" (BBC News, August 10, 2026).
This is a textbook example of how corporate language masks concrete action: from 62.5 grams to 40 — this isn't a "pack size update," it's a 22-gram reduction, meaning roughly 35% of the chocolate from the bar disappeared quietly. No one got an explanation why it happened exactly this way — the press release works like diffuse fog.
The main non-obvious fact: shrinkflation isn't a 21st-century corporate invention. It's the oldest trick in the food economics book.
In feudal Europe, when grain prices rose, bakers faced a choice: raise the price of bread or sell a smaller loaf for the same money. They chose the latter — not out of greed, but out of fear. Bread prices in the 13th century weren't set by the market but by the canonical doctrine of "just price" from Thomas Aquinas: basic products should sell at prices accessible to most of the community. This price was enforced by moral sanctions — and the threat of bread riots: "urban plebeians, confronted with excessive bread prices, rioted against magistrates, looted granaries, and killed bakers" (Witold Kula, Measures and Men, 1970, the classic work on the history of measurement).
When price is fixed by custom, the only way out is reduce the portion. Bakers had no other option. In this sense, the Mars from Scunthorpe is a direct descendant of the medieval baker from Paris: the price per bar is a marker of "just price" in modern form, and any increase triggers political noise, while silent weight reduction doesn't.
In modern history, this logic formalized as a business technique. The most cited legend in marketing — about American Airlines in the '80s: the company saved $40,000 a year (real money then) by removing one olive from economy-class salads. Nobody noticed. The legend became a symbol of cost-saving wizardry in business textbooks, but it's precisely shrinkflation, just nicely named (NYT, 2001).
The terminology was systematized by economist Pippa Malmgren in the early 2000s, and Brian Domitrovic used a similar word earlier — to describe an economy shrinking during high inflation (Merriam-Webster). By the 2010s shrinkflation went mainstream: in Britain the ONS recorded 206 products that decreased in size versus 79 that increased in the 2015–2017 period (UK Office for National Statistics, 2019).
Underlying all this is a fundamental discovery from experimental psychology — Weber's Law (1834) and the derived concept of just-noticeable difference (JND). The law states: perceived difference is proportional to the original stimulus, meaning the bigger the bar, the more you need to take away for a person to notice. In practice this means:
Manufacturers balance between these two thresholds like a pilot between two walls in a narrow gorge: take away a bit more — they'll notice, raise price a bit more — they'll notice. The ideal strategy — take away from weight as much as you can without crossing the JND threshold.
This isn't theory — it's empirics measured on big data. Ian Meeker (FTC) and Jakob von Ditfurth (Mannheim), using NielsenIQ Retail Scanner and Consumer Panel data from 35,000 American stores and 60,000 households, showed with McCormick Black Pepper:
Chicago Booth Review (Spring 2025): "Manufacturers looking to contain overheads and grow profits face a dilemma. They can shrink their products and hope customers don't notice, or increase prices and cross their fingers."
When the problem went public, states started reacting. France — the pioneer: on July 1, 2024 a decree from the Ministry of Economy (April 16, 2024) took effect, requiring retailers in large and medium supermarkets to place an information notice near the product for 2 months after a weight/volume change if the unit price rises. Applies to bottled water, rice, laundry detergent, canned goods, both brands and private label. Doesn't apply to pre-packaged foods with variable weight or bulk goods. Bruno Le Maire, economy minister, said when issuing the decree: "The practice of shrinkflation is a scam! We're stopping it. I want to restore consumer confidence, and confidence comes with transparency" (Ministère de l'Économie, April 18, 2024).
Austria went further — in April 2026 the Anti-Deceptive Packaging Law took effect (Schoenherr, April 2026). Brazil required label updates when quantity changes (UL Solutions, April 2026). In the US S.3819 — Shrinkflation Prevention Act 2024 — remains a bill with no movement (congress.gov, May 22, 2024). President Biden in 2023–2024 used the term in political rhetoric, accusing corporations of "greedflation," but this didn't lead to federal regulation.
In Britain the ONS already in 2019 recorded that 206 products decreased in size versus 79 increased — and this without law, just statistics. After Brexit the country didn't adopt the French model, but Carrefour in France starting September 2023 voluntarily warns customers about shrinkflation — the first case in Europe where a major chain itself started flagging the practice (Merkur, September 2023).
It's not just Mars Bar. The global shrinkage map, per Wikipedia/St Louis Fed:
Economist Barak Orbach formulated this crystal clear: "When supply shocks or other factors increase production costs, business must pass cost increases to consumers to maintain profitability. In competitive markets, however, directly raising prices is risky. Under such conditions, business often chooses indirect price increases — through size reduction" (ProMarket, 2023).
Macroeconomist Vivek Moorthy (before the term "shrinkflation" existed) described this through Arthur Okun's "invisible handshake": "Prices are based on notions of trust and fairness. It's considered acceptable when firms respond to cost increases, but not to demand increases. Firms selling branded products make conscious efforts to maintain price and retain loyal customers. Therefore to combat inflation FMCG companies resort to reducing product size" (Applied Macroeconomics, IK International, 2017).
Two mechanisms work simultaneously: the manufacturer wants to preserve shelf price as long as possible because it's a psychological anchor (remember Mars Bar — 35 years the same shelf price in a British supermarket), and the consumer is three times more sensitive to price than volume due to perception peculiarities. At the intersection of these two mechanisms the perfect environment is born for quiet, unnoticed value redistribution.
In 2020 McCormick paid $2.5 million in a class action for "nonfunctional slack-fill" — empty space in packaging that misled buyers about quantity. This is the first major precedent where slack-fill became legal grounds for a lawsuit. Meaning the shrinkflation mechanism has a built-in limiter: if you leave the package the same size and just pour less product inside, there's risk of legal prosecution.
Toblerone in 2016 changed the shape — increased the gap between mountain "peaks" so the bar visually stayed similar but mass decreased. This is smarter than slack-fill: the product geometry changes, and formally there are fewer complaints. But this only worked because aesthetic habit outweighed quantity.
Mars Bar shrank by 22 grams over 35 years — that's 35% mass loss. This is already on the edge of the perception threshold. The next 5 years will be interesting: either Mars returns to larger size (as some brands did under social media pressure), switches to new package format, falls under France's 2024 law (if it spreads to EU), or gets a class action like McCormick.
Here's where the story gets really interesting. Slate (2022) points to the paradox: shrinkflation is based on consumers not tracking weight with the same precision as price. But this only works short-term. McCormick could quietly cut pepper volume 25% in 2015, but by 2020 consumers started understanding they were being shortchanged — and filed a class action.
Meaning shrinkflation is a delayed bomb. It works while people have short memory and no accurate scales at home. When you have:
— the math starts breaking down. Weber's Law hasn't gone anywhere, but JND became smaller: 22 grams in 1991 were below threshold, but in 2026 — no longer, because viral context emerged.
This explains why shrinkflation is accelerating right now: companies see the window of opportunity closing (laws, lawsuits, social media) and are trying to squeeze maximum before regulation becomes mandatory.
This isn't about a chocolate bar. This is about a fundamental perception asymmetry that corporations have been monetizing for 700 years — since 13th-century Parisian bakers and Thomas Aquinas. The 1991 Mars Bar was 62.5 grams not because cocoa was cheaper in 1991 or corporations kinder — but because consumers hadn't yet learned to count grams, and the state hadn't yet learned to demand packaging transparency.
What we're seeing in 2026 is the final stage of this 700-year cycle. Mars Bar shrunk to 40 grams, McCormick got hit with a $2.5M class action, France introduced mandatory notices, Austria introduced anti-deceptive packaging law. Once bakers could be killed in the street for shrinking a loaf; now they face class actions, fines, or just public humiliation through a viral photo on social media. The cycle closes, but in softer form.
What hooked me most — the structural similarity of shrinkflation with Okun's "invisible handshake". Price is a public contract with the consumer. Volume is a private variable nobody checks. Any economy where the public contract is stricter than the private variable breeds shrinkflation as an inevitable side effect. Medieval Paris, post-Soviet Russia, modern London — the same formula works everywhere.
And here's what I'll say as an engineer: this is one of the most elegant examples of "laws of psychology being weaponized for margin" that I know. Not because of the scale of deception — but because of its invisibility. This isn't viral customer shortchanging at checkout, this is gradual, 5–7% per cycle value extraction, so smooth the consumer only notices when accumulated delta becomes photographable.
If in the next five years the EU extends the French model EU-wide and the US passes the Shrinkflation Prevention Act — we'll see the end of a 700-year era. If not — corporations will squeeze another 20 years until the last consumer buys pocket scales.
📎 Sources: BBC News (August 10, 2026), Wikipedia/Shrinkflation, Slate (August 26, 2022), Chicago Booth Review (Spring 2025), UK Office for National Statistics (2019), St Louis Fed (December 2022), Bird & Bird (July 2024), Ministère de l'Économie (April 18, 2024), ConfectioneryNews (November 13, 2015), Witold Kula Measures and Men (1970), ProMarket (August 18, 2023), Vivek Moorthy Applied Macroeconomics (IK International, 2017), Ken Alder The Measure of All Things (Simon & Schuster), JDSupra (2020), Tom's Hardware (September 2025), Merkur (September 2023), Schoenherr (April 2026).