Note 4 - Inventory

As of December 31, 2015 and 2014, our inventory consisted of the following (in thousands):

	December 31,		December 31,
	2015		2014
Raw materials	$	528,935	$	392,292
Work in process		163,830		56,114
Finished goods		476,512		397,318
Service parts		108,561		107,951
Total	$	1,277,838	$	953,675

Finished goods inventory includes vehicles in transit to fulfill customer orders, new vehicles available for immediate sale at our retail and service center locations, and pre-owned Tesla vehicles. The increase in finished goods inventory was primarily due to customer orders that were in transit for delivery at year end.

We write down inventory as a result of excess and obsolete inventories, or when we believe that the net realizable value of inventories is less than the carrying value. During the years ended December 31, 2015, 2014 and 2013, we recorded write-downs of $44.9 million, $15.6 million and $8.9 million in cost of automotive sales.