Tim Wood helps us remember the 7 types of waste, but he does not teach us about prioritizing the elimination of the 7 types of waste. "TIM WOOD" stands for Transportation, Inventory, Motion, Waiting, Overproduction, Over-processing, Defects but this is by no means the priority in which to attack the wastes. The following is a more common sense approach.

Priority #1. Overproduction is the worst of the wastes because a) it multiplies the other 6 wastes, and b) it hides your true capacity, thereby causing you to make bad decisions such as turn work away or invest in unnecessary additional capacity.

Priority #2. Defects come next because it is as close to pure waste as you can get when you produceunacceptably poor quality. Time, energy and materials are consumed needlessly, and if the customer is not lost, you still need to do the work again.

Priority #3. Inventory is a good candidate for the next worst of the 7 wastes. It ties up cash, requires labor, energy and fixed assets (warehouse) to manage it, and perhaps worst of all provides a false sense of comfort by hiding problems (buffering).

Priority #4. Motion waste is a close candidate for inclusion in the top 3, and may even be number one if the human movements are injurious or unsafe. In terms of ease of elimination and size of improvement impact, the waste of motion ranks very high and is often the target of kaizen.

Priority #5. Processing waste simply means that a process is not necessary or uses more resources (energy, steps, time or materials) then the customers' needs require. These are quick wins once identified, and can be high impact but are not as common as the other 6 types of waste.

Priority #6. Transportation is quite visible and clearly adds no value, yet by itself not such a huge waste. This waste can shoot up the priority list whenever it increases the chance of defects (damage), processing (tagging, logging items in and out, counting) and creating inventory (moving in batches to save travel).

Priority #7. Waiting is the least harmful because at least you are not consuming resources other than labor, and by not overproducing, transporting, or wasting motion the chance of accidents, defects and creating additional inventory is minimized. As hard as it may be, it is best to tell people "Wait, don't overproduce" so that they can pull the andon cord and make the problem visible.

This list is manufacturing-oriented. For healthcare, defects is by far the first highest priority waste for all out elimination. Defective parts you can scrap or correct, but people not so much. For various other types of knowledge work, the relatively high cost of labor and low cost of materials brings waiting and processing to the top of the list and may move inventory down the list. For distribution operations whose main value is storing and moving things, inventory and transportation may need to be understood differently to give meaningful priority to attacking the 7 types of waste.

Getting rid of the 7 types of waste is fundamental to the Toyota Production System and to building a Lean culture in any enterprise. There is no clear prioritizing by badness of the 7 types of waste in the classic TPS literature, and deep debate on this topic is probably time that could be better spent making even one small improvement on the gemba.