state a key rule of lean as, “Every customer-supplier
connection must be direct, and there must be an unambiguous yes-or-no way to send
requests and receive responses”. Companies that use push-based production face
ambiguity about what independent variables to use, how to apply them in forecast
calculations and the extent that forecasts should be adjusted based on “expert opinion”.
Even if System 2 thinking is used to help develop a forecast, detrimental System 1 biases
can skew its analysis, interpretation and application. In contrast, pull production based
purely on downstream demand and simple visual methods such as kanbans support
unambiguous data-driven decision-making. Pull production’s simplicity may make it
seem less attractive than forecasting methods that are more complex, but its simplicity
is its strength. It incorporates beneficial reliance on immediate customer demand into
System 1 thinking that simultaneously excludes the use of harmful System 1 biases that
work their way into forecasts. Although lean companies still use forecasts (e.g. for
long-range planning of capacity), responsiveness enabled in part by pull production
does more to help organizations meet customer requirements than relying on detailed
short-term forecasting that is prone to inaccuracies.