Launched in 1986, the Big Mac index is based on the theory of purchasing-power parity (PPP), which says that exchange rates should move to make the price of a basket of goods the same in each country.
The magazine's 'basket' contains just a single item, a Big Mac hamburger, sold in 120 countries around the world. The exchange rate that leaves a Big Mac costing the same in dollars everywhere is used as a fair-value yardstick.
1.2 billion buttered-ham sandwiches sold in 2008
Mimicking the Big Mac PPP structure, Gira Conseil will use its 'ham-butter' (jambon-beurre) index to compare the prices of the enduringly popular ham sandwich in each region of France and every distribution circuit. They hope the indice will be a "true reference for the buying power of French consumers."
In 2008, the french chewed their way through 1.2 billion buttered-ham sandwiches, representing about 70 per cent of the overall 1.8 billion sandwiches eaten in France.
Each year Gira Conseil will publish a report compiling the prices of the buttered-ham sandwich in France, allowing observers to ultimately track the evolution of French buyer power over the previous 12 months.
"Is there a big difference in price between big and small towns? Does geographical location make a difference to price? Can certain distribution circuits adapt to the recession to capture new business?" asks Gira Conseil.
They claim three elements stand as a backdrop to the new index. Firstly, prices in France for a typical ham sandwich range from €1.79 spotted at a hypermarket, to more than double this price - €3.72 - at an upmarket sandwich shop, claim the analysts.
Secondly, cafes, the traditional home of the ham sandwich, have been unable to adapt to the evolving market for sandwiches, failing to realise the positioning of the sandwich as a key product to bring in the consumers. Further, they have lost potential consumers by pitching their sandwiches in a high price bracket.
Finally, bakers in France have witnessed a strong growth in sales for their sandwiches. In just a few years, the bakers have gained 14 per cent of the total €6.1bn sandwich market, the result of "a strong understanding of price and positioning", said the french analysts.
The index methodology
In total, the first index launched this year used data from 704 selling stations. In terms of methodology, Gira Conseil divided France into 22 regions, with two towns in each region selected, one big, and one with fewer than 50 000 inhabitants.
Creating a 'complete picture', the market researchers said compiled data from eight distribution channels – including independent bakers, cafes, independent sandwich shops and hypermakets.