if one steps back to assess the current situation in american industry, it is clear that the concept of "lean manufacturing" is widely embraced for competitive purposes.
This means that lean firms increasingly buy more and make less. A rule of thumb used by some firms is to outsource subsystems and components unless they fall into one of the following three categories
1. An item that is critical to the success of the product, including customer perceptions of important product attributes.
2. An item that requires specialized design and manufacturing skills or equipment and for which the number of capable and reliable suppliers is extremely limited.