Limitations of Weight Based System:
* It cannot easily estimate cost differentials below gross levels of the work breakdown structure (WBS) . This precludes the method from being useful for trade-off studies of designs, materials, and manufacturing processes.
* It cannot estimate cost differentials of outfit work performed at different stages of construction: on unit,on block and on board. Various established rules of thumb indicate that these cost differentials can vary from 300% to 500% or more.
* It cannot estimate cost differentials due to configuration complexity, such as compartment or system density (e.g. HVAC system installation in tight deckhouse) or location on board the ship (e.g. confining engine room installation versus easily accessible weather deck installation).
* It cannot estimate cost differentials due to orientation of work (e.g. less productive over head work versus more productive down hand work).
* It cannot estimate cost differentials due to changes in build strategy, including outsourcing the manufacturing of selected components to more productive, less costly vendors and suppliers.
* Since it operates mostly at high levels of the WBS, it cannot easily translate or segment costs from one type of ship to another, particularly ship types and hull forms not yet developed and built.
In typical government fashion, although it is clear that a Paleolithic cost estimating system is being used, little is being done to improve the current situation.