The cheese, the rats – and why some of us are poorer than others

8th June, 2023

In a laboratory in College Station, Texas, in 1990, six lab rats pressed levers and lapped at tubes as root beer and tonic water were released. They were participating in the quest for an elusive quarry: the Giffen good.

Robert Giffen was born in Lanarkshire in 1837, the year of Queen Victoria’s accession. He would become by turns assistant editor at The Economist, chief statistician at the Board of Trade, President of the Royal Statistical Society and co‑founder of the Royal Economic Society. An eminent Victorian indeed, even if one biographer sniffed, “He was one of those figures . . . whose not inconsiderable power and prestige appears to be disproportionate to their actual contribution to economic science.” Ouch.

Yet Giffen’s name is known to every economics student. This is not because of the research he published, but because of a thought experiment which reached his contemporary Alfred Marshall, who put it in his inescapable textbook Principles of Economics. The idea is that certain goods might be consumed more when their prices rise, because the increased cost backs consumers into a corner.

Here’s how I imagined it, as an impoverished student. My staple diet was jacket potatoes with cheese or tuna mayo, bought from a nearby kebab van. Imagine that the price of potatoes rose. Ordinarily, I’d be expected to buy fewer potatoes and more of something else. The problem is everything else was still more expensive than potatoes. With my budget squeezed, I couldn’t afford the luxury of the cheese and tuna topping. The missing calories would come from . . . more potatoes.

In this example, potatoes are a “Giffen good”. Potatoes were a major part of my diet; when their price rose, I effectively became poorer and switched towards the cheapest foodstuff. The cheapest foodstuff was potatoes. Of course, this did not actually happen. I was never that destitute and never such a potatophage.

For about a century, economists looked for real examples of Giffen goods and did not find them until 1990, when economists Raymond Battalio, John Kagel and Carl Kogut demonstrated Giffen behaviour in lab rats. (The lab rats, I am assured, were well looked after by Battalio’s neighbour, a vet.) The researchers offered the rats quinine-flavoured water, which the rats disliked, and root beer, which they loved. The effective prices of these drinks were changed by adjusting the volume of drink released each time the rat pressed a lever. Root beer was “expensive” because it was dispensed in smaller portions.

And sure enough, it proved possible to provoke Giffen behaviour: when the cheaper quinine water became less cheap, rats still needed a drink and they cut back on the luxury of root beer, drinking more quinine water.

So are Giffen goods little more than a theoretical curiosity? Not quite. Eventually, the economists Robert Jensen, Nolan Miller and Sangui Wang used both public health data and a field experiment to demonstrate that in the poorest parts of Hunan, China, rice was a Giffen good. As Jensen wrote in 2008, “It’s funny that people have looked in crazy places for Giffen behaviour . . . and it turns out that it could be found in the most widely consumed food in the most populous nation in the history of humanity.”

Giffen goods also teach us something important about the impact of price rises on the poorest people. One of the most basic lessons of economics is that people respond to price hikes by finding cheaper options. If apples are expensive this week, buy oranges; when the price of oranges rises and the price of apples falls, switch back to apples again. Or just look for the bargain-basement option. If a West End show is too expensive, go to the cinema. If the cinema costs too much, watch television. You don’t have to pay higher prices; you can make do with a cheaper alternative.

Inflation is always a little lower than it seems once you allow for such substitutions. But one group of people can’t play that game: those who are already relying on the cheapest staples have nowhere to run from price rises.

So it wasn’t quinine water in a Texas laboratory, or rice in Hunan, that made me think recently of Giffen goods. It was the alarming rise in the price of a cheese salad sandwich. The latest data from the UK show that sliced white bread has risen in price by 29 per cent over the past 12 months, with tomatoes up 16 per cent, butter up 30 per cent, cheddar cheese up 42 per cent and cucumber 55 per cent more expensive. (Headline inflation, meanwhile, is just over 10 per cent.)

I am not claiming that cheddar cheese is essential to life; it just seems that way. Nor is it a Giffen good. But basic foodstuffs are Giffen-adjacent. They are the last resort of people who cannot afford fancier stuff. Food poverty campaigners — most prominently Jack Monroe — have argued that the price of these basics has risen much faster than the general rate of inflation.

As I’ve written before, it’s hard to be sure if that’s true. The Office for National Statistics tends to focus on the most popular products, not the cheapest bargains, and so the relevant data is patchy and experimental.

Whether or not inflation really is higher for the poorest households, what is not in doubt is that inflation hits them hardest. That is both because they are more vulnerable, and because they have less room for manoeuvre as they ponder their options in the supermarket aisle. The Bank of England’s chief economist, Huw Pill, recently said that, “We’re all worse off.” Maybe so. But some of us are worse off than others.

Written for and first published in the Financial Times on 12 May 2023.

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