Inventories

9 Months Ended

Sep. 30, 2021

3. INVENTORIES

Inventories consisted of the following (in millions):


	September 30, 2021		December 31, 2020
Refinery feedstocks	$	1,646	$	1,979
Refined petroleum products and blendstocks	3,944		3,425
Renewable diesel feedstocks and products	113		50
Ethanol feedstocks and products	233		297
Materials and supplies	291		287


Inventories	$	6,227	$	6,038

We compare the market value of inventories to their cost on an aggregate basis, excluding materials and supplies. In determining the market value of our inventories, we assume that feedstocks are converted into refined products, which requires us to make estimates regarding the refined products expected to be produced from those feedstocks and the conversion costs required to convert those feedstocks into refined products. We also estimate the usual and customary transportation costs required to move the inventory from our plants to the appropriate points of sale. We then apply an estimated selling price to our inventories. If the aggregate market value is less than the aggregate cost, we recognize a loss for the difference in our statements of income. To the extent the aggregate market value of our last-in, first-out (LIFO) inventories subsequently increases, we recognize an increase to the value of our inventories (not to exceed cost) and a gain in our statements of income.

The market value of our LIFO inventories fell below their LIFO inventory carrying amounts as of March 31, 2020, and as a result, we recorded an LCM inventory valuation reserve of $2.5 billion in order to state our inventories at market. As of September 30, 2020, we reevaluated our inventories and determined that our cost was lower than market. As a result, our LCM inventory valuation reserve was fully reversed as of September 30, 2020. The change in our LCM inventory valuation reserve resulted in a net benefit of $313 million during the three months ended September 30, 2020. The net benefit of $19 million for the nine months ended September 30, 2020 was due to the foreign currency translation effect of the portion of the LCM inventory valuation adjustment attributable to our international operations. As of September 30, 2021 and December 31, 2020, the replacement cost (market value) of LIFO inventories exceeded their LIFO carrying amounts by $5.2 billion and $1.3 billion, respectively.

During the three and nine months ended September 30, 2020, we recognized the impact of an expected liquidation of LIFO inventory layers that increased cost of materials and other by $326 million. Our LIFO inventory levels decreased throughout the first nine months of 2020 due to lower production resulting from lower demand for our products caused by the negative economic impacts of the COVID-19 pandemic on our business. Consequently, we expected our LIFO inventory levels as of December 31, 2020 would remain below their December 31, 2019 levels.

Our non-LIFO inventories accounted for $1.2 billion and $918 million of our total inventories as of September 30, 2021 and December 31, 2020, respectively.