After lunch, the hikers begin again, though Alex notices that they’ve rearranged themselves according to speed. The fastest boys take the lead, and Herbie brings up the rear in front of Alex. This only makes the line of hikers stretch out more quickly, however. Although everyone else can hike at whatever speed they want, Alex has to slow to Herbie’s pace. Alex realizes that this means the slowest member of the group thus governs the overall pace of the group. It doesn’t matter how fast the fastest kids are—Alex, at the back (representing the group’s throughput) can only move as fast as the slowest variable.
This organization of hikers represents the manufacturing system when it is set up to allow for the maximum efficiency of each worker and machine—each hiker (or stage in the manufacturing process) can operate at its full capacity 100 percent of the time, since no one in front is slow enough to create a constraint. However, the fact that the hikers immediately spread thin implies that inventory skyrockets, losing money for the plant and making this an unsustainable way to organize.
A sign marker along the trail indicates that they still have five miles to go, meaning that the hikers have been moving an average speed of one mile per hour, rather than two. However, realizing that the slowest variable governs the pace of the group gives Alex an idea. He shouts up the trail for everyone to stop hiking and hold their place in line. When everyone is together, Alex reverses the order of the line so that Herbie hikes in front and the fastest kids are in the back. When the fast kids complain, Alex explains that he’s not trying to make them fast, but to keep them hiking together.
Just as the first order of hikers meant that nobody was ever constrained by anyone else, this reverse order ensures that everyone is constrained, which means that their individual efficiencies are low. However, if the group can stay together, the short distance between Herbie in the front and Alex in the back suggests that their inventory stays as low as possible, which is ideal. Thus, a system that appears inefficient actually wastes less money than an efficient system.
As the hikers begin again, Alex is pleased to see that they stay together as a group for the first time. Each hiker is capable of matching the speed of the boy in front of him. Soon after, the boys behind Herbie notice how heavy his pack is and divide up some of his gear for him. Without the extra weight, Herbie can hike faster and the whole troop moves along at a good pace, all staying together. Alex thinks, “Inventory is down. Throughput is up.” They reach their destination and Alex calculates that after reorganizing, the hikers achieved their proper average speed of two miles per hour. As they make camp and settle in for the night, Dave asks Alex how he knew to reorganize, and Alex shares what he learned on the hike.
The other hikers dividing up Herbie’s gear and allowing him to hike faster represents Alex increasing the capacity of his chief constraint, his bottleneck, which allows the entire system to move faster. By pacing according to the slowest hiker, the hikers maintain a consistent, sustainable speed for everyone which creates fewer delays and allows for a higher average pace. Alex’s realization that inventory decreases while throughput increases suggests that with this organization, his plant will become more profitable.