Related Party Transactions

The significant related party transactions occurring during the years ended December 31, 2018, 2017 and 2016 are described below. We believe all of our transactions with Glencore and BHH were at prices that approximate market.

Glencore ownership

As of December 31, 2018, Glencore plc and its affiliates (together "Glencore") beneficially owned 42.9% of Century’s outstanding common stock (47.2% on a fully-diluted basis assuming the conversion of all of the Series A Convertible Preferred Stock) and all of our outstanding Series A Convertible Preferred stock. See Note 7. Shareholders' Equity for a full description of our outstanding Series A Convertible Preferred stock. From time to time Century and Glencore enter into various transactions for the purchase and sale of primary aluminum, purchase of alumina, tolling agreements and certain forward financial contracts.

Sales to Glencore

For the year ended December 31, 2018, we derived approximately 64% of our consolidated sales from Glencore. Glencore purchases the aluminum we produce for resale.

Glencore purchases aluminum produced at our North American smelters at prices based on the LME plus the Midwest regional premium and any additional negotiated product premiums. Glencore purchases aluminum produced at our Grundartangi, Iceland smelter at prices based on the LME plus the European Duty Paid premium and any applicable product premiums.

In 2016, we were party to a tolling arrangement with Glencore that provided for delivery of primary aluminum produced at Grundartangi. We received tolling fees from Glencore under this tolling agreement based on the LME price for primary aluminum plus a portion of the European Duty Paid premium.

Purchases from Glencore

We purchase a portion of our alumina requirements from Glencore. Alumina purchases from Glencore during 2018 were priced based on a published alumina index.

Transactions with BHH

We own a 40% stake in BHH and have an agreement to purchase carbon anodes from them for use in our manufacturing operations. We have begun a project to rebuild one of our baking furnaces at Vlissingen, which is expected to increase annual carbon anode production capacity by an additional 12,000 tonnes per year. The rebuilt baking furnace is expected to be operational before the end of 2019. We expect to meet the requirement of carbon anodes at Grundartangi through Vlissingen and BHH.

Summary

A summary of the aforementioned significant related party transactions for the years ended December 31, 2018, 2017 and 2016 is as follows:



	Year Ended December 31,
	2018		2017		2016
Net sales to Glencore	$	1,204.5	$	1,198.1	$	1,178.6
Purchases from Glencore	319.6		253.0		231.9
Purchases from BHH	28.4		15.8		10.1