Zara computed every store's replenishment by size and lifted sales 3–4%

Zara replenishes about 1,500 stores worldwide from just two central warehouses, and fast fashion's short lifecycles meant stores frequently had the wrong sizes on the shelf. Stockout and markdown losses followed, but store managers had no way to see the demand link for each size.

Zara deployed a new process that uses sophisticated operations research models to determine every inventory shipment it sends to each store. The model takes a size-assortment view of store inventory, connects stock levels to demand, and decides replenishment quantities per store and size, overcoming significant technical and human resistance during deployment.

A controlled field experiment estimated the new process increased sales by 3–4 percent, worth roughly $233 million in profits and $353 million in additional revenues for 2007 and 2008. The work made Caro, Gallien and Zara colleagues Franz Edelman laureates in the 2009 competition.