Note 5. Inventories

Our available-for-sale inventory amounts by product type were as follows at the dates indicated:

	March 31, 2013		December 31, 2012
NGLs	$	531.4	$	594.3
Petrochemicals and refined products		443.3		304.5
Crude oil		165.6		119.4
Natural gas		18.8		70.2
Total	$	1,159.1	$	1,088.4

In those instances where we take ownership of inventory volumes through percent-of-liquids contracts and similar arrangements (as opposed to outright purchases from third parties for cash), these volumes are valued at market-based prices during the month in which they are acquired.

Due to fluctuating commodity prices, we recognize lower of cost or market adjustments when the carrying value of our available-for-sale inventories exceeds their net realizable value. These non-cash charges are a component of cost of sales in the period they are recognized. To the extent our commodity hedging strategies address inventory-related price risks and are successful, these inventory valuation adjustments are mitigated or offset. See Note 4 for a description of our commodity hedging activities.

The following table presents our total cost of sales amounts and lower of cost or market adjustments for the periods indicated:

	For the Three Months
	Ended March 31,
	2013		2012
Cost of sales (1)	$	9,692.5	$	9,665.8
Lower of cost or market adjustments	$	2.7	$	5.9
(1) Cost of sales is a component of "Operating costs and expenses," as presented on our Unaudited Condensed Statements of Consolidated Operations. Quarter-to-quarter fluctuations in these amounts are primarily due to changes in energy commodity prices and sales volumes associated with our marketing activities.