Its not just the lost sale of the specific out-of-stock items that are at risk in a competitive market though. Over time their customers will notice that freque

Its not just the lost sale of the specific out-of-stock items that are at risk in a competitive market though. Over time their customers will notice that frequently one or two items they need are out of stock, but when they go to the competitor to get those missing items, they always have them. So they start shopping at the competitor to begin with and rarely have reason to return to the original store since everything is always in stock. Now the original store has lost most of the sales they used to get from that customer. It similar to why not offering vegetarian food at a restaurant can have a much larger impact on sales than just the loss of the small number of vegetarian purchases - you loose out on the entire group that came with the vegetarian.