The humble Mars bar, once Britain’s most reliable economic barometer, has finally succumbed to the forces of modern capitalism. For generations, we used the price of a Mars bar as our go-to metric for understanding the value of money and tracking inflation. It was beautifully simple – a tangible way to grasp abstract economic concepts that made sense to everyone from schoolchildren to economists.
But shrinkflation has well and truly killed our beloved Mars bar index. The steady reduction in size whilst maintaining price has rendered it useless as a consistent measure of value. In 2008, a Mars bar weighed 62.5 grams and cost 35p[1]. Today, you’ll pay £1.05 for just 51 grams of chocolate, nougat and caramel[2][3]. That represents a staggering price per gram increase from 0.56p to 2.06p – a near four-fold jump that tells us more about corporate strategy than economic reality.
The Golden Years of the Mars Bar Index
Let me take you back to when the Mars bar index actually worked. The concept gained serious academic attention after Nico Colchester’s observation in the Financial Times back in 1981 that Mars bars represented a remarkably stable unit of account[4]. He noted that small cars had cost roughly 20,000 Mars bars consistently for 70 years – now that’s what I call a reliable benchmark.
The beauty of the Mars bar as an inflation measure lay in its standardised nature and mass appeal. Unlike complex economic indicators that require advanced degrees to understand, anyone could grasp the significance of a Mars bar doubling in price over a decade. It was the people’s currency, if you will.
The Price History That Tells a Story
Looking at the comprehensive price history I’ve compiled, we can trace the Mars bar’s journey from affordable treat to premium indulgence. In 1957, you could buy one for 2.5 pence (sixpence in old money)[5]. By 1970, it had crept up to 3p[6], staying remarkably stable through the early seventies. The real acceleration began in the eighties – jumping from 15p in 1980 to 20p by 1985[6].
The nineties saw more modest increases, with prices hovering around 25-30p through most of the decade[5][7]. But then came the new millennium, and with it, the beginning of the end for our chocolate-covered economic indicator.
The most dramatic changes occurred after 2008. Not only did prices begin climbing more steeply, but manufacturers started playing the shrinkflation game. Mars reduced their bar from 62.5g to 58g in 2008, then down to 51g in 2013[8], all whilst maintaining similar price points. This corporate sleight of hand effectively broke the Mars bar as a reliable measure.
The Shrinkflation Problem
Shrinkflation has become the corporate world’s favourite trick for managing rising costs without appearing to raise prices. It’s particularly insidious because it requires consumers to do mental arithmetic to spot what’s happening. Most people notice when a Mars bar jumps from 50p to 60p, but far fewer notice when it shrinks from 58g to 51g whilst staying at 50p.
Mars Inc. justified their size reductions as part of their “Responsibility Deal” commitment to reduce calories, claiming they were tackling obesity[8]. Whilst public health is undoubtedly important, one can’t help but notice how convenient this was for their profit margins during a period of soaring commodity costs.
The company faced particularly severe cost inflation in recent years. Analysis by Mintec showed that the cost of producing an average milk chocolate bar soared by 25% year-on-year in 2013[8], adding 6p to the cost of making a 100g bar. The main culprit was rocketing cocoa butter prices, hit by adverse weather in the Ivory Coast.
What Could Replace the Mars Bar Index?
With our chocolate champion fallen, where do we turn for an accessible inflation measure? Several contenders emerge, each with their own merits and drawbacks.
The Big Mac Index
The Economist’s Big Mac Index, launched in 1986, remains the most famous alternative[9]. It compares the price of McDonald’s Big Mac burgers across different countries and over time, based on the theory that identical products should cost the same everywhere after adjusting for exchange rates.
Currently, a Big Mac costs £5.49 in the UK[10], and whilst McDonald’s has occasionally tweaked portion sizes, the Big Mac has remained relatively consistent compared to our poor Mars bar. The index benefits from global reach and standardised preparation, making it useful for international comparisons.
However, the Big Mac faces its own challenges. McDonald’s operates in only 111 of 195 countries[11], limiting its global applicability. More importantly for our domestic inflation tracking, Big Mac prices can be influenced by factors specific to the fast-food industry, such as minimum wage legislation, property rental costs in high-traffic locations, and McDonald’s own corporate pricing strategies.
The Pint Price Index
Few things are more fundamentally British than a pint down the pub, making beer prices an intriguing alternative. As of July 2025, the average pint costs £5.17[12] – a figure that varies dramatically by region, from under £3.50 in Preston to over £6 in London[13].
Pint prices have the advantage of reflecting multiple economic factors: grain costs, energy prices, taxation, wages, and property costs. They’re also something most adults can relate to and remember. The price of beer has outpaced both inflation and average salary increases, rising 15.8% over 2023-2024 compared to inflation of 9.8%[14].
The challenge with pint prices lies in their regional variation and the influence of government policy. Beer duty, VAT, and licensing costs can create artificial price movements unrelated to underlying inflation. The closure of pubs – 239 in the first quarter of 2024 alone[13] – also complicates the picture by reducing competition in some areas.
The Costa Coffee Index
Our coffee culture has exploded over the past two decades, making a regular latte a common purchase for millions. A regular latte at Costa currently costs £4.40[15], having risen from £2.25 in 2018[16] – a 95% increase that far exceeds official inflation figures.
Coffee prices benefit from reflecting global commodity markets (coffee beans), local labour costs, property rental, and consumer discretionary spending. They’re also relatively standardised across locations, though airport and station outlets typically charge premiums[16].
The downside is that coffee prices can be volatile due to weather conditions affecting crop yields, and they don’t represent essential spending for everyone. They’re also influenced by the competitive dynamics between coffee chains and changing consumer preferences.
The Newspaper Conundrum
Traditionally, newspaper prices served as excellent inflation indicators, but declining readership has made them less representative of general spending patterns. The ONS removed newspaper advertising from their inflation basket[17], reflecting this broader trend away from print media.
The Freddo Factor
Some have suggested the Cadbury Freddo as a Mars bar replacement. These mini chocolate frogs have certainly experienced dramatic price inflation – rising from 10p in 2000 to 25p today (with a brief peak at 30p in 2017)[18]. However, Freddos suffer from the same shrinkflation issues as Mars bars and represent an even smaller, more specialised market segment.
The Modern Reality of Measuring Inflation
The truth is that no single product can perfectly capture the complexity of modern inflation. The ONS maintains a basket of over 700 goods and services[17], regularly updated to reflect changing consumption patterns. Their 2025 additions include virtual reality headsets and exercise mats, whilst removing items like DVD rentals and newspaper adverts[19].
This sophisticated approach recognises that inflation affects different people differently. Energy costs hit older people on fixed incomes hardest, whilst younger consumers might be more affected by housing costs or technology prices. Food inflation particularly impacts lower-income households who spend a higher proportion of their income on necessities[20].
The ONS approach also attempts to account for quality changes – something our simple Mars bar index never could. When products improve over time, some price increases reflect better value rather than pure inflation[21].
What This Means for You
As someone who’s spent years advising businesses and individuals on financial matters, I’d suggest developing your own personal inflation index. Track the prices of items you buy regularly – whether that’s your weekly shop, monthly fuel bill, or annual holiday costs.
Pay particular attention to the price per unit rather than headline prices. That £1 bag of sugar might seem like good value until you notice it’s dropped from 1kg to 800g. The same applies to everything from breakfast cereals to washing powder[22].
Consider keeping a simple spreadsheet with key prices from your monthly shop. Not only will this help you spot inflation in your own spending, but it might reveal opportunities to switch products or retailers when relative prices change.
For businesses, the lesson is clear: transparency about pricing changes tends to work better than attempting to hide them through shrinkflation. Consumers are becoming increasingly savvy about these tactics[23], and social media means that size reductions are quickly noticed and shared.
The Broader Economic Picture
The death of the Mars bar index reflects broader changes in our economy. We’ve moved from a world of relatively stable products and gradual price changes to one of constant innovation, complex supply chains, and sophisticated pricing strategies.
Modern businesses have tools that would have seemed like science fiction to the Mars bar manufacturers of the 1970s. They can track consumer behaviour in real-time, adjust prices dynamically, and test different packaging sizes to optimise profitability. This sophistication makes simple price comparisons increasingly difficult.
We’re also dealing with unprecedented global interconnectedness. A drought in the Ivory Coast affects chocolate prices in Birmingham[1]. Supply chain disruptions in Asia impact everything from electronics to clothing. Energy price volatility, driven by geopolitical events thousands of miles away, ripples through every sector of our economy.
Moving Forward Without Our Chocolate Compass
Whilst we mourn the loss of the Mars bar as our reliable economic compass, we shouldn’t despair. The principles that made it useful – simplicity, universality, and relevance to everyday life – can guide us towards better alternatives.
I’d argue for a portfolio approach: track a few key items that matter to you personally, understand their limitations, and use them alongside official statistics to build a rounded picture of economic change. Your personal inflation rate might differ significantly from official figures, and that’s perfectly normal[19].
The Big Mac Index will likely continue serving economists and international observers well[24]. For domestic purposes, pint prices offer a quintessentially British alternative that reflects multiple economic pressures. Coffee prices capture our modern consumer culture whilst remaining relatable to millions.
Perhaps most importantly, the Mars bar’s demise teaches us to remain vigilant about corporate practices. When companies resort to shrinkflation rather than honest pricing, they’re essentially hoping consumers won’t notice. By staying informed and making conscious choices, we can send clear signals about what we find acceptable.
The Sweet Conclusion
The Mars bar index served us well for over half a century, providing a simple way to understand complex economic concepts. Its death by shrinkflation marks the end of an era – one where products remained largely unchanged and price comparisons were straightforward.
In our more complex economic landscape, we need more sophisticated tools and approaches. But we shouldn’t lose sight of the Mars bar index’s greatest strength: it made economics accessible to everyone.
Whether we adopt the Big Mac Index, create our own basket of everyday items, or simply become more conscious consumers, the goal remains the same – understanding how economic forces affect our daily lives. The Mars bar might have lost its economic relevance, but the lessons it taught us about staying informed and engaged remain as important as ever.
The next time you see a Mars bar on the shelf, spare a thought for its service to economic education. Then check the price per 100g and marvel at how far we’ve come from the days when inflation tracking was as simple as remembering what you paid for your favourite chocolate bar.
Further Reading and References
[1] What’s the we cheapest you remember a Mars bar costing? – Reddit https://www.reddit.com/r/AskUK/comments/abaaw2/whats_the_we_cheapest_you_remember_a_mars_bar/
[2] Some Mars Bar inflation calculations : r/rickygervais – Reddit https://www.reddit.com/r/rickygervais/comments/1lpsfg8/some_mars_bar_inflation_calculations/
[3] Mars bar – Wikipedia https://en.wikipedia.org/wiki/Mars_bar
[4] Spending calculator: Which prices are rising and falling fastest? https://news.sky.com/story/spending-calculator-which-prices-are-rising-and-falling-fastest-12588123
[5] Chocolate bars: manufacturers’ sales price UK 2008-2023 – Statista https://www.statista.com/statistics/481698/chocolate-bars-value-weight-in-the-united-kingdom-uk/
[6] Standard single mars bar cost – Page 1 – The Lounge – PistonHeads https://www.pistonheads.com/gassing/topic.asp?h=0&f=210&t=2079435
[7] The Freddo (and Mars, and Beano) Index – Vouchercloud https://www.vouchercloud.com/better-living/the-freddo-index
[8] UK inflation: Chocolate price rises hit record as food costs grow – BBC https://www.bbc.co.uk/news/articles/c5ygdqp922vo
[9] Mars bars shrink but price stays the same | News – The Grocer https://www.thegrocer.co.uk/news/mars-bars-shrink-but-price-stays-the-same/352754.article
[10] Inflation – Written in the Mars? – Arlingclose https://www.arlingclose.com/insights/inflation—written-in-the-mars
[11] Does inflation reflect the size of Mars Bars? – Tim Harford https://timharford.com/2009/06/does-inflation-reflect-the-size-of-mars-bars/
[12] Lipstick, Underwear And Mars Bars – Economic Analysis – Jersey https://www.mondaq.com/jersey/economic-analysis/693644/lipstick-underwear-and-mars-bars
[13] Mars Inflation Index – LinkedIn https://www.linkedin.com/pulse/20140903150249-28684-mars-inflation-index
[14] Shrinkflation strikes again as Galaxy chocolate gets smaller – BBC https://www.bbc.co.uk/news/business-66924100
[15] UK retailers report Mars Bar shortage, amid record levels of food … https://www.confectioneryproduction.com/news/40844/uk-retailers-report-mars-bar-shortage-amid-record-levels-of-food-sector-price-inflation/
[16] Galaxy cuts chocolate bar size in latest ‘shrinkflation’ to hit shoppers https://www.standard.co.uk/business/business-news/galaxy-cuts-chocolate-bar-size-in-latest-shrinkflation-to-hit-shoppers-b1109624.html
[17] The Mars bar downsizes once again : r/unitedkingdom – Reddit https://www.reddit.com/r/unitedkingdom/comments/3217b8/the_mars_bar_downsizes_once_again/
[18] Size Matters: Is Shrinkflation Stealing Our Chocolate? – Appliance City https://www.appliancecity.co.uk/news/updates/is-our-chocolate-getting-smaller/
[19] The maths of shrinkflation – how your food could be getting smaller https://www.mathscareers.org.uk/the-maths-of-shrinkflation-how-your-food-could-be-getting-smaller/
[20] Mars Bars – 51g (Box of 24) – Vending Superstore https://vendingsuperstore.co.uk/products/mars-bars-box-of-24
[21] Does BIGMAC Index Consider as a Substitute for Inflation Rate https://journalofbusiness.org/index.php/GJMBR/article/view/2983
[22] Mars Chocolate Bar (51g) – Compare Prices & Where To Buy – Trolley https://www.trolley.co.uk/product/mars-caramel-nougat-milk-chocolate-snack-bar/MBM229
[23] The Big Mac Index and Overall Consumer Inflation | St. Louis Fed https://www.stlouisfed.org/on-the-economy/2024/apr/how-big-mac-index-relates-overall-consumer-inflation
[24] Mars Milk Chocolate Bar 51G – Tesco Groceries https://www.tesco.com/groceries/en-GB/products/314315107
[25] Big Mac Index – Wikipedia https://en.wikipedia.org/wiki/Big_Mac_Index
Mars Bar Index
| Year | Price (pence) | Weight (grams) | Price per gram (pence) | Comments |
|---|---|---|---|---|
| 2025 | 105.0 | 51.0 | 2.059 | Current price at major retailers |
| 2024 | 85.0 | 51.0 | 1.667 | Supermarket price |
| 2023 | 51.0 | 51.0 | 1.000 | RRP maintained after size reduction |
| 2022 | 51.0 | 51.0 | 1.000 | During high inflation period |
| 2018 | 51.0 | 51.0 | 1.000 | After 2013 size reduction |
| 2013 | 51.0 | 58.0 | 0.879 | Before major size reduction |
| 2010 | 40.0 | 58.0 | 0.690 | Pre-shrinkflation period |
| 2008 | 35.0 | 62.5 | 0.560 | Before first major size reduction |
| 2000 | 30.0 | 62.5 | 0.480 | Turn of millennium |
| 1997 | 30.0 | 62.5 | 0.480 | Late 1990s pricing |
| 1990 | 25.0 | 65.0 | 0.385 | Early 1990s |
| 1985 | 20.0 | 68.0 | 0.294 | Mid-1980s |
| 1980 | 15.0 | 65.0 | 0.231 | Early 1980s |
| 1976 | 4.0 | 60.0 | 0.067 | Mid-1970s |
| 1973 | 3.0 | 60.0 | 0.050 | Early 1970s |
| 1970 | 3.0 | 60.0 | 0.050 | Start of decade |
| 1965 | 2.5 | 55.0 | 0.045 | Pre-decimal currency (6d) |
| 1957 | 2.5 | 55.0 | 0.045 | Pre-decimal currency (6d) |
Big Mac Index
| Year | Price (£) | Price (USD) | Annual increase (%) | Comments |
|---|---|---|---|---|
| 2025 | £5.39 | $6.85 | 3.7% | Current UK menu price (burger only) |
| 2024 | £5.20 | $5.90 | 6.3% | Big Mac Index data |
| 2023 | £4.89 | $5.71 | 8.2% | Big Mac Index data |
| 2022 | £4.52 | $5.27 | 29.5% | During high inflation period |
| 2020 | £3.49 | $4.89 | 9.4% | December 2020 data |
| 2019 | £3.19 | $4.71 | 18.6% | July 2019 data |
| 2013 | £2.69 | $4.18 | 17.5% | June 2013 data |
| 2008 | £2.29 | $3.21 | 18.0% | May 2008 data |
| 2005 | £1.94 | $2.58 | -2.5% | May 2005 data |
| 2002 | £1.99 | $2.35 | 4.7% | March 2002 data |
| 2000 | £1.90 | $2.24 | 9.2% | Start of millennium |
| 1996 | £1.74 | $2.80 | 45.0% | Student meal deal era |
| 1992 | £1.20 | $2.10 | 9.1% | Early 1990s estimate |
| 1990 | £1.10 | $1.95 | 15.8% | Based on historical data |
| 1986 | £0.95 | $1.60 | 46.2% | Big Mac Index launch year |
| 1980 | £0.65 | $1.20 | 51.2% | Early UK McDonald’s |
| 1974 | £0.43 | $0.85 | – | First UK McDonald’s opened |
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