When most people look at designer bags, what do you think is the first thought that comes to mind? I'd wager it would be along the lines of "nice, but absolutely not at that price". And that very moment of hesitation could actually tell us more about the economy than you might think.Now, a luxury bag isn't like groceries or petrol. It is a want, not a need. But when people start thinking twice about those purchases, it is worth thinking about the bigger picture and whether consumer confidence is taking a hit.According to Citi's credit card data released earlier this month, luxury spending fell 6% year-on-year in September. And that follows from the declines of 4% in both July and August before that. The data shows three consecutive months of weakness. So, that is not exactly encouraging especially when wealthy US consumers have been one of the more resilient groups in this economy.Having said that, let's take a look at this. US retail sales actually rose by 0.8% in September, albeit largely bolstered by higher gasoline prices. But in excluding gasoline stations, retail sales still grew by 0.2%.It's not extravagant but it still suggests that US consumers are still spending. However, that doesn't necessarily mean they are buying more stuff. It just means that their spending habits have perhaps changed.So, how does this tie back to Wall Street?Just imagine that you are running a luxury retailer. You've got expensive stores, employees and marketing bills to pay. And those costs don't disappear just because fewer customers are buying handbags. As such, slower sales mean less revenue to cover those expenses. And if you turn to promotions to attract customers, then your profit margins could get squeezed further.Now, I'm not suggesting fewer handbag purchases mean a recession is coming. Luxury spending is only one piece of the consumer puzzle, and the wealthiest shoppers tend to behave differently from everyone else.But if that hesitation starts spreading to the likes of clothing, electronics, travel and other discretionary purchases, then corporate earnings forecasts could be next in line for a reality check. And when investors start questioning how much consumers are really willing to spend, stock valuations can suddenly look rather expensive.With that in mind, it's worth noting that sometimes the first economic warning can simply just be what is sitting unsold on a store shelf. And it could very well be the designer bag that the crowd chooses to pass on. This article was written by Justin Low at investinglive.com.