The four criteria for assessing class importance apply to cairnfields as follows:
- Period (currency): Long-lived. The majority of dates from cairnfields fall within the period 1750 BC to 450 BC, and this seems to represent the main period of cairnfield development. A small number of cairnfields result from activities which took place during early/middle Neolithic times, while others have medieval and post-medieval associations.
This chronology is based on a very small sample of dated sites. Little is known about the duration of individual cairnfields or the rate of accumulation because no systematic dating programme has been applied to the separate components of a single example. It may, however, be assumed that most cairnfields were used over fairly long periods of time.
- Rarity: Common. Over 250 cairnfields have been recorded to date, but this figure is not the result of systematic survey and is certainly biased by knowledge (and publication) of the larger and more accessible sites. Where systematic surveys have taken place it appears that between 60% and 80% of cairnfields comprise less than 30 clearance cairns. Thus the complete coverage of all regions with cairnfields is likely to increase substantially the numbers known.
- Diversity (types): Medium. Four main types of cairnfield have been distinguished on the basis of size and internal arrangement. The individual component clearance cairns found within cairnfields may belong to one or more of the four main kinds cairn defined on the basis of ground plan. Diversity is further increased by examples of this monument class being located in a variety of topographic situations.
- Period (representativity): High. Because of the long period over which cairnfields were constructed the determination of this criterion must represent an average for the lifespan of the class as a whole, which ranges from very high in Neolithic times through to medium in later prehistoric and medieval times.
Assigning scores to these criteria following the system set out in the Monument Evaluation Manual, cairnfields yield a Class Importance Value of 33. This lies about mid-way up the range of possible values (max.= 64). In selecting examples which are of national importance it is important to include examples that represent a variety of topographic and geological situations. A representative sample of the types defined above is also desirable. Examples of different date should be included wherever possible.