Many fashion retailers in the US seem to be permanently on discount. Among the forces that have contributed to this state of affairs is a fundamental shift in the relationship between supply and demand, spurred by the spread of e-commerce, social media, and the new shopper behavior they’ve encouraged.

The issue of endless discounting is a big one for brands. It cost them some $300 billion last year. It squeezes their margins, and over time, chips away at their cachet. In the past, fashion was largely a supply-led market, meaning, brands and retailers put the products they wanted into stores, on schedules they chose. Consumers then bought up what was available at the shops they had access to.

But then the internet came along. Consumers today can shop anywhere. A steady stream of images and products in their social feeds drives a ravenous desire for new products. Demand, not supply, has become the controlling force.

This change has put brands in the position of always trying to keep up with an appetite for newness, but many still haven’t figured out how to do it efficiently. Often the long lead times of their supply chains mean they still have to produce huge amounts of clothing months in advance to fill their shops, leaving them guessing far ahead of time what shoppers will want, and not always accurately. They can get stuck with large and costly amounts of overstock.