THE usual assumption is that the stock market is a “leading indicator” for economic confidence. But as today’s cut of YouGov data shows, it doesn’t lead public sentiment, but is actually behind.<br /><br />The graph shows the BrandIndex scores for public perception of “value for money” (rolling monthly average) for Waitrose, J Sainsbury and M&S, alongside the FTSE 100.<br /><br />There is a strong correlation between them, at least until the end of last year. The correlations rise significantly when we shift the FTSE to one month forward.<br /><br />As with the data we looked at last week in this space, about petrol brands, what’s interesting here is both the similarity and differences between the tracks. For three years, the brands move pretty much in tandem. But more recently, they have significantly diverged.<br /><br />The explanation may be in how the supermarkets responded to the credit crunch. Sainsbury’s moved first to protect its brand. In September 2008 the “Switch & Save” campaign was launched, encouraging customers to buy Sainsbury’s own brands over other, more expensive products.<br /><br />As we can see, this campaign quickly had an effect. Consumers began to view Sainsbury’s as better value-for-money. By the beginning of June its scores were as high as high as Lidl, Aldi and Morrisons.<br /><br />M&S moved next, launching its “Plan A Way to Save” scheme in January. This told customers that by making “Green” changes they could save £1,000 over the course of a year. It was less successful than the Sainsbury’s campaign, but did produce a steady increase in M&S value scores. Waitrose was last to get in on the act with its “essentials” range launched in March. Waitrose has seen an improvement in its value scores but it is still scoring lower than its rivals on this measure.<br /><br />Stephan Shakespeare is co-founder and chief innovation officer of polling firm YouGov.