Product Sales

Net product sales consist of the following:



	Three Months Ended June 30,				Six Months Ended June 30,
Net Product Sales in the United States	2018		2017		2018		2017
EYLEA^®	$	991,998	$	919,466	$	1,976,047	$	1,773,853
ARCALYST^®	4,384		4,667		8,244		8,525
	$	996,382	$	924,133	$	1,984,291	$	1,782,378

The Company had product sales to certain customers that accounted for more than 10% of total gross product revenue for each of the three and six months ended June 30, 2018 and 2017. Sales to each of these customers as a percentage of the Company's total gross product revenue are as follows:



	Three Months Ended June 30,				Six Months Ended June 30,
	2018		2017		2018		2017
Besse Medical, a subsidiary of AmerisourceBergen Corporation	56	%	50	%	55	%	51	%
McKesson Corporation	35	%	29	%	37	%	28	%
Curascript SD Specialty Distribution, a subsidiary of Express Scripts	**		20	%	**		20	%
** Sales to Curascript SD Specialty Distribution represented less than 10% of total gross product revenue during the period.

Revenue from product sales is recognized at a point in time when our customer is deemed to have obtained control of the product, which generally occurs upon receipt by our distributors and specialty pharmacies. The Company's written contracts with its customers stipulate product is shipped freight on board destination (FOB destination).

The amount of revenue we recognize varies due to rebates, chargebacks, and discounts provided under governmental and other programs, distribution-related fees, and other sales-related deductions. We estimate the amount of variable consideration that we will be entitled to, in order to determine the transaction price, based upon contracts with customers and government agencies, statutorily-defined discounts applicable to government-funded programs, historical experience, estimated payer mix, and other relevant factors.

The following table summarizes the provisions, and credits/payments, for these sales-related deductions during the six months ended June 30, 2018 and 2017.



	Rebates, Chargebacks, and Discounts			Distribution- Related Fees			Other Sales- Related Deductions			Total
Balance as of December 31, 2017	$	29,840		$	34,142		$	21,320		$	85,302
Provisions	97,698			102,133			19,892			219,723
Credits/payments	(91,108		)	(98,532		)	(24,431		)	(214,071		)
Balance as of June 30, 2018	$	36,430		$	37,743		$	16,781		$	90,954

Balance as of December 31, 2016	$	12,712		$	29,465		$	3,674		$	45,851
Provisions	78,250			90,077			20,531			188,858
Credits/payments	(67,850		)	(90,519		)	(21,312		)	(179,681		)
Balance as of June 30, 2017	$	23,112		$	29,023		$	2,893		$	55,028

Accruals for chargebacks and discounts are recorded as a direct reduction to accounts receivable. Accruals for rebates, distribution-related fees, and other sales-related deductions are recorded within accrued liabilities.