What are the main effects of the bullwhip effect on a Supply Chain?

The main effects are inventory inflation (30 to 60% above what stable demand would require), service-level degradation (because the inflated stock sits in the wrong tier), capacity whiplash at suppliers (idle plants alternating with overtime), expediting costs, and forecast accuracy collapse upstream. Working capital is the financial symptom: cash parked in raw-materials and component inventory while finished goods stock out. The same network often experiences excess and shortage at the same time, in different tiers, for the same product family.