Business developments can be hard to predict; for instance, a customer could place an unexpectedly large order for one of your products. That should be great news for you–but only if you’re prepared to fill the order on time. That’s where safety stock comes in.

Forecasting precisely how much inventory you’ll need is always a difficult proposition; safety stock, by acting as “buffer inventory,” allows businesses to build up some margin for error. The downside, of course, is that holding inventory–let alone extra inventory–is expensive.

Some studies have pegged it at 20–40 percent of the cost of stocked merchandise. Making matters worse: That’s an ongoing, recurring cost, not a one-off purchase.…