6.	INVENTORIES

Inventories are valued at the lower of cost or net realizable value using a FIFO inventory method. Inventory is comprised of implants and instruments held for sale, including implants consigned or loaned to customers and agents. The consigned or loaned inventory remains our inventory until we are notified of the implantation. We are required to maintain substantial levels of inventory because it is necessary to maintain all sizes of each component to fill customer orders. The size of the component to be used for a specific patient is typically not known with certainty until the time of surgery, and certain sizes are typically used less frequently than the “standard” sizes. Due to this uncertainty, a minimum of one of each size of each component in the system to be used must be available to each sales representative at the time of surgery, including unusual sizes that will be sold less frequently than “standard” sizes. Although we may conclude that it is more likely than not that all quantities on hand of certain sizes will eventually not be sold, we do not consider such items “excess inventory,” as our business model requires that we maintain such quantities in order to sell the “standard” sizes. As a result of the need to maintain substantial levels of all sizes and components of inventory, we are subject to the risk of inventory obsolescence. In the event that a substantial portion of our inventory becomes obsolete, it would have a material adverse effect on the Company.

An allowance charge for slow moving inventories is recorded based upon an analysis of slow moving inventory items within a product group level. The slow moving inventory allowance is analyzed and calculated based on comparing the current quantity of inventory to historical sales and provides an allowance for any slow moving inventory on a systematic basis, which recognizes the cost of anticipated future obsolescence over the average fifteen year expected life of product groups. We believe this method is appropriate as it recognizes the lack of utility of these items (as a charge to cost of goods sold) over the related product group revenue life cycle. The key inputs to our slow moving allowance are trailing twelve months usage and the expected product life. Due to the nature of slow moving inventory changes in sales patterns from historical trends and future product release schedules, this could impact our allowance analysis. For items that we identify as obsolete, we record a charge to reduce their carrying value to net realizable value. We also maintain an allowance for discrepant inventory to allow for items that are lost or damaged. Allowance charges for the three and nine months ended September 30, 2016 were $1.1 million and $3.4 million, respectively. Allowance charges for the three and nine months ended September 30, 2015 were $1.4 million and $3.5 million, respectively.

We also test our inventory levels for the amount of inventory that we expect to sell within one year. Due to the scope of products required to support surgeries and the fact that we stock new subsidiaries, add consignment locations, and launch new products, the level of inventory often exceeds the forecasted level of cost of goods sold for the next twelve months. We classify our estimate of such inventory as non-current.

The following table summarizes our classifications of inventory as of September 30, 2016 and December 31, 2015:


(in thousands)	September 30, 2016		December 31, 2015
Raw materials	$	21,437	$	19,481
Work in process		1,609		1,633
Finished goods on hand		16,524		14,497
Finished goods on loan/consignment		50,337		44,813
Inventory total		89,907		80,424
Non-current inventories		12,341		8,995
Inventories, current	$	77,566	$	71,429