(Note that the first letter of each of these wastes spells the acronym “TIMWOOD“.)
The one element that is notably missing from this list is the human factor. For that reason, many people add an eighth waste to the original seven. There are several different versions of this eighth waste, but all focus on wasting the potential or ability of team members.
The most common ‘eighth wastes’ are:
There is a bit of debate about whether or not there should be 8 wastes. Some purists don’t like the idea of adding to the original Ohno/Shingo wastes. Others feel that they would be supportive of the change if it added something of value.
Regardless of whether you use 8 wastes or 7, though, it is a problem if you leave human potential untapped. Not only is it disrespectful to people to not give them a challenging, rewarding job, but it also leaves money on the table. The more brains you have attacking other forms of waste, the better.