We operate in one business segment: human therapeutics. Therefore, results of our operations are reported on a consolidated basis for purposes of segment reporting, consistent with internal management reporting. Revenues by product and by geographic area, based on customers’ locations, are presented below. Rest-of-world (ROW) revenues relate to products that are sold primarily in Europe.



	Year ended December 31, 2019
	U.S.		ROW		Total
Enbrel^®(etanercept)	$	5,050	$	176	$	5,226
Neulasta^®(pegfilgrastim)	2,814		407		3,221
Prolia^®(denosumab)	1,772		900		2,672
XGEVA^® (denosumab)	1,457		478		1,935
Aranesp^®(darbepoetin alfa)	758		971		1,729
KYPROLIS^®(carfilzomib)	654		390		1,044
EPOGEN^® (epoetin alfa)	867		—		867
Sensipar^®/Mimpara^® (cinacalcet)	252		299		551
Other products	2,907		2,052		4,959
Total product sales⁽¹⁾	16,531		5,673		22,204
Other revenues	693		465		1,158
Total revenues	$	17,224	$	6,138	$	23,362



	Year ended December 31, 2018
	U.S.		ROW		Total
ENBREL	$	4,807	$	207	$	5,014
Neulasta^®	3,866		609		4,475
Prolia^®	1,500		791		2,291
Aranesp^®	942		935		1,877
XGEVA^®	1,338		448		1,786
Sensipar^®/Mimpara^®	1,436		338		1,774
EPOGEN^®	1,010		—		1,010
KYPROLIS^®	583		385		968
Other products	1,947		1,391		3,338
Total product sales⁽¹⁾	17,429		5,104		22,533
Other revenues	929		285		1,214
Total revenues	$	18,358	$	5,389	$	23,747



	Year ended December 31, 2017
	U.S.		ROW		Total
ENBREL	$	5,206	$	227	$	5,433
Neulasta^®	3,931		603		4,534
Aranesp^®	1,114		939		2,053
Prolia^®	1,272		696		1,968
Sensipar^®/Mimpara^®	1,374		344		1,718
XGEVA^®	1,157		418		1,575
EPOGEN^®	1,096		—		1,096
KYPROLIS^®	562		273		835
Other products	1,419		1,164		2,583
Total product sales⁽¹⁾	17,131		4,664		21,795
Other revenues	898		156		1,054
Total revenues	$	18,029	$	4,820	$	22,849

^____________

In the United States, we sell primarily to pharmaceutical wholesale distributors that we utilize as the principal means of distributing our products to healthcare providers. Outside the United States, we sell principally to healthcare providers and/or pharmaceutical wholesale distributors depending on the distribution practice in each country. We monitor the financial condition of our larger customers and limit our credit exposure by setting credit limits and, in certain circumstances, by requiring letters of credit or obtaining credit insurance.

We had product sales to three customers, each of them accounting for more than 10% of total revenues for each of the years ended December 31, 2019, 2018 and 2017. For the year ended December 31, 2019, on a combined basis, these customers accounted for 81% of total gross revenues as shown in the following table. Certain information with respect to these customers was as follows (dollar amounts in millions):



	Years ended December 31,
	2019			2018			2017
AmerisourceBergen Corporation:
Gross product sales	$	12,301		$	12,091		$	10,742
% of total gross revenues	33		%	33		%	31		%
McKesson Corporation:
Gross product sales	$	11,795		$	11,434		10,625
% of total gross revenues	31		%	31		%	30		%
Cardinal Health, Inc.:
Gross product sales	$	6,538		$	7,475		$	7,049
% of total gross revenues	17		%	20		%	20		%

As of December 31, 2019 and 2018, amounts due from these three customers each exceeded 10% of gross trade receivables and accounted for 73% and 76%, respectively, of net trade receivables on a combined basis. As of December 31, 2019 and 2018, 27% and 23%, respectively, of trade receivables, net, were due from customers located outside the United States, the majority of which were from Europe. Our total allowance for doubtful accounts as of December 31, 2019 and 2018 was not material.