The headline is a weighted composite of new orders, production, employment, supplier deliveries and inventories. Being first out of the gate each month gives it outsized market impact for a survey covering a sector that is roughly a tenth of employment.
The internals matter more than the headline. New orders minus inventories is a forward-looking spread, and the prices paid component is one of the better early reads on goods inflation. Supplier delivery times rise both when demand is booming and when supply chains are broken, so read that one in context.
Example: the headline prints 48.2 with new orders at 51.4 and inventories at 45.0. The index is technically contracting, but orders exceeding inventories by 6.4 points implies restocking ahead and often marks a turn.
Related: pmi, ism-services-pmi, sp-global-pmi, diffusion-index, industrial-production