A-items are goods which annual consumption value is the highest. The top 70-80% of the annual consumption value of the company typically accounts for only 10-20% of total inventory items.

C-items are, on the contrary, items with the lowest consumption value. The lower 5% of the annual consumption value typically accounts for 50% of total inventory items.

B-items are the interclass items, with a medium consumption value. Those 15-25% of annual consumption value typically accounts for 30% of total inventory items.

Please check your classification... 

1) Let's start by explaining the need to use the ABC classification:

When there are large number of items in stock, one solution to facilitate the management of the inventory is to group similar items in order to have a single policy for the category instead of a different policy for each item. The well know ABC classification technique is about sorting inventory items to one of 3 predefined and ordered categories(i.e. classes): category A contains the very important items, category B includes the moderately important items and category C contains the relatively unimportant items.

2) The second thing to bear in mind is that traditional ABC analysis uses the annual dollar usage (ADU) criterion to classify inventory items into one of the three categories. Nevertheless, recent literature have showed that many other criteria may be significant and should be involved in the item classification process (e.g. ordering cost, criticality, lead time, obsolescence, substitutability, order size requirement, etc.). Considering more than one criterion, the ABC analysis is performed on the basis of the items global performance. This performance expressed by a weighted score that combines the item evaluation on the different criteria and the criteria weights. Items are then ordered in a descending order of their weighted score. Finally, the top 5% - 10% of items constitute category A (items with highest scores), the next 20% - 30% of items are classified in category B, and category C will contain 50% - 70% of items (items with lowest scores).

3) In my previous papers, I used two different inventory performance evaluation methods from the literature, to evaluate my proposed ABC classification.

 a.  The total relevant cost (TRC), you can read about it in this paper:            https://www.researchgate.net/publication/301199366_A_New_Multi-                 Criteria_ABC_Inventory_Classification_Model_Based_on_a_Simplified_Electre_III_Method_and_the_Continuous_Variable_Neighborhood_Search         

 b. Inventory cost and fill rate measures: you can read about it in this paper: https://www.researchgate.net/publication/303843768_A_New_Model_for_Multi-criteria_ABC_Inventory_Classification_PROAFTN_Method          

I hope my answer will help. Best regards.

Conference Paper A New Multi-Criteria ABC Inventory Classification Model Base...

Conference Paper A New Model for Multi-criteria ABC Inventory Classification:...

ABC analysis is the best and simple tool available for inventory management. By categorization of inventory on the basis of annual value usage in the concerned industry.

The ABC analysis has to focus on Value and criticality rather than quantum. It is a simple concept that has helped process improvements and optimization particularly in manufacturing industry.