‘Pull’ vs. ‘Push’: economies of flow vs. economies of scale
However, what Ohno saw and what the Americans saw when they looked at this crucible of modern mass production were remarkably different. At the plant, work was standardized in a simple, unchanging flow. When Ohno studied the plant, that’s what he saw—a unified flow. As each car rolled off the line, it represented to him a ‘heartbeat’ that dictated how everything moved (was ‘pulled’) through the system in a single stream. Today at Toyota the customer order triggers flow: nothing is made without an order, and the customer receives the car within days. Toyota’s aim is constant improvement of the flow—producing cars at the rate of demand, the cumulative effect of which is that by the 1990s it took Toyota fewer man hours to build a Lexus than it did a top-line German manufacturer to rework a model at the end of the production line, after it had been made (Womack et al., 1990). Shortly before he died, Ohno was asked what he was working on; ‘shortening the time between the receipt of the customer order and collecting the money,’ he replied.