Priority on line side productivity

Why give priority to line side productivity? The assembly line is the place where value is created. It is also the place with the highest labour density.
Finally, the line is the most expensive place in terms of production costs, labour density and plant investment.
So priority must be given to line side production because the line is where added value is created.

One of the golden rules of Lean is that Mudas must be eliminated as much as possible from the point of added value, i.e. assembly points.
We shall see for example how Mudas must be "moved" from the line to upstream processes, so that it can then be reduced…