6. Inventories

Inventories are valued at the lower of cost or market for last-in, first-out (“LIFO”) inventory and lower of cost or net realizable value for first-in, first-out (“FIFO”) inventory. Approximately 30 percent of inventories are valued using the LIFO method of determining cost. All other inventories are valued at the FIFO method of determining cost. An actual valuation of inventory under the LIFO method can be made only at the end of each year based on inventory levels and costs at that time. Accordingly, interim LIFO calculations must necessarily be based on management’s estimates of expected year-end inventory levels and costs. Because these are based on estimates, interim results are subject to change in the final year-end LIFO inventory valuation. During the current year, one inventory pool had a reduction in inventory quantities that is expected to hold through year-end, and therefore an adjustment was recorded for the nine months ended September 30, 2018 to decrease cost of sales by $0.5 million as a result of the liquidation of LIFO inventories. No adjustment was recorded for the three months ended September 30, 2018 as the estimated interim LIFO adjustment was not material.

In the prior year, one inventory pool had an increase in commodity costs that was expected to hold through year-end, and therefore, an adjustment of $0.4 million was made to increase the LIFO reserve and cost of sales for the three and nine months ended September 30, 2017.

Inventories consisted of the following:

	September 30,		December 31,
	2018		2017
Finished and in-process products	$	28,772	$	31,307
Raw materials and supplies		15,538		15,859
	$	44,310	$	47,166