Supply chain planning is the process of aligning what a company expects to sell with what it can produce, source, and deliver — across four time horizons simultaneously. When it works, it reduces inventory while improving service. When it fails, companies hold too much of the wrong product and too little of the right one at the same time.
Most supply chain leaders can describe supply chain planning. Far fewer can say why their version of it consistently fails to prevent the inventory surprises, expedite costs, and service failures that show up quarter after quarter.
The reason is almost always the same: they are treating supply chain planning as a single process when it is actually four distinct processes operating at four different time horizons — each asking a completely different question, each requiring different data, and each making decisions that the others depend on.
When a company collapses these four horizons into a single monthly S&OP meeting, they produce a hybrid document that answers none of the four questions well. Strategic decisions get made without the capital analysis they require. Operational decisions get deferred because the meeting runs out of time. Execution problems get elevated to leadership when they should have been caught at the operational level. The result is a planning process that everyone attends and nobody finds useful.
