Inventories

12 Months Ended

Dec. 31, 2020

Inventories at December 31, 2020 and 2019 were as follows (in millions):


	2020		2019
Raw materials and supplies	$	207.6	$	164.9
Work-in-process	690.7		899.6
Finished goods	181.6		161.3
Total inventories at current cost	1,079.9		1,225.8
Adjustment from current cost to LIFO cost basis	44.1		33.6
Inventory valuation reserves	(126.9)		(104.1)
Total inventories, net	$	997.1	$	1,155.3

Inventories determined on the LIFO method were $627.5 million at December 31, 2020, and $776.1 million at December 31, 2019. The remainder of the inventory was determined using the FIFO and average cost methods, and these inventory values do not differ materially from current cost. Due to deflationary impacts primarily related to raw materials, the carrying value of the Company’s inventory as valued on LIFO exceeds current replacement cost, and based on a lower of cost or market value analysis, the Company maintains net realizable value (NRV) inventory valuation reserves to adjust carrying value of LIFO inventory to current replacement cost. These NRV reserves were $44.1 million and $33.6 million at December 31, 2020 and 2019, respectively. In applying the lower of cost or market principle, market means current replacement cost, subject to a ceiling (market value shall not exceed net realizable value) and a floor (market shall not exceed net realizable value reduced by an allowance for a normal profit margin).

Impacts to cost of sales for changes in the LIFO costing methodology and associated NRV inventory reserves were as follows (in millions):


	Fiscal year ended December 31,
	2020		2019		2018
LIFO benefit (charge)	$	10.5	$	25.5	$	(28.6)
NRV benefit (charge)	(10.5)		(25.6)		27.9
Net cost of sales impact	$	—	$	(0.1)	$	(0.7)

During 2020 and 2019, inventory usage resulted in liquidations of LIFO inventory quantities, increasing cost of sales by $22.6 million and $1.8 million, respectively. During 2018, inventory usage resulted in liquidations of LIFO inventory quantities, decreasing cost of sales by $0.8 million. These inventories were carried at differing costs prevailing in prior years as compared with the cost of current manufacturing cost and purchases.