The complexity of technology based products within the healthcare field demands a logical approach to market sizing.  The sizing must be consistent regardless of the end use application of a product.  Such an approach was utilized during the mid 1970's by Abbott Laboratories AD&D division to better define markets, based upon a specific technology.  Abbott emphasized,  the "sustaining advantage" of the product's technology eventually translates into real economic terms becoming one of the fundamental reasons for product purchase. The approach allowed for a product assessment, based upon technology, to be better compared or contrasted against existing products or services already successfully fulfilling a specific customer need within a market place.  Abbott's approach provided a basis for "refined segmentation" that subsequently led to mathematical algorithms being used, resulting in a more objective assessment of the market segments of interest.  

The PAM (Potential Available Market) is largely dependent upon the marketer's "view of the world". The TAM (Total Available Market) is used to define the entire accessible market for a given product's technology upon which a company's product is based. There may be any number of SAM's (Served Available Market), each representing a different technology, composing the TAM.   Each company's product's technology is part of a specific SAM. There may be more than one company marketing a product with a similar technology within a SAM.  Each company's product is represented by the an individual SOM (Share of Market).  The SOM being specific to an individual company represents that company's product's market share position

The basic Tenets of the PAM/TAM/SAM/SOM relationship:

1. The TAM is never greater than the PAM (TAM < PAM)

2. The SAM is never greater than the TAM and may be equal to the TAM (SAM = to or < TAM)     

3. The SOM is never greater than the SAM and may be equal to the SAM (SOM= to or < SAM).

The TAM never equals the PAM (TAM < PAM).