Note 7. Inventories

Our inventory amounts by product type were as follows at the dates indicated:

	December 31,
	2013		2012
NGLs	$	593.8	$	594.3
Petrochemicals and refined products		395.1		304.5
Crude oil		42.6		119.4
Natural gas		61.6		70.2
Total	$	1,093.1	$	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 6 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 Year Ended December 31,
	2013			2012			2011
Cost of sales (1)		$	40,770.2		$	36,015.5		$	38,292.6
Lower of cost or market adjustments		$	18.5		$	22.1		$	9.5

(1)	Cost of sales is a component of "Operating costs and expenses," as presented on our Statements of Consolidated Operations. Year-to-year fluctuations in these amounts are primarily due to changes in energy commodity prices and sales volumes associated with our marketing activities.