A bottleneck (or constraint) in a supply chain means the resource that requires the longest time in operations of the supply chain for certain demand. Usually, phenomena such as increase of inventory before a bottleneck and insufficiency of parts after a bottleneck are often seen. Statistically, since fluctuations are inconsistent, the phenomena (excess inventory and insufficient materials) do not always occur. In the case of hiking, a bottleneck means the slowest member in walking. An interval between the bottleneck member and the one before spreads, and narrows with the one after.
An important thing about bottlenecks is that bottlenecks determine the throughput of a supply chain. If a bottleneck person in hiking can walk faster, the speed of the whole group will increase. Similarly, if the capacity of a bottleneck in a supply chain improves, the throughput will increase. From the definition of bottlenecks, the operating rate of non-bottlenecks is below 100%. If so, the operating rate of non-bottlenecks will increase only within 100% even if the capacity of the bottleneck increases and the throughput increases. If the operating rate of non-bottlenecks exceeds 100%, it means that the bottleneck place is moved to the place of non-bottlenecks.