7. EMPLOYEE BENEFIT PLANS

A majority of WESCO’s employees are covered by defined contribution retirement savings plans for their services rendered subsequent to WESCO’s formation. WESCO also offers a deferred compensation plan for select individuals. For U.S. participants, WESCO matches contributions made by employees at an amount equal to 50% of participants' total monthly contributions up to a maximum of 6% of eligible compensation. For Canadian participants, WESCO makes contributions in amounts ranging from 3% to 5% of the participants' eligible compensation based on years of continuous service. WESCO may also make, subject to the Board of Directors' approval, a discretionary contribution to the defined contribution retirement savings plan covering U.S. participants if certain predetermined profit levels are attained. For the nine months ended September 30, 2017 and 2016, WESCO incurred charges of $20.3 million and $18.1 million, respectively, for all such plans. Contributions are made in cash to employee retirement savings plan accounts. The deferred compensation plan is an unfunded plan. As of September 30, 2017 and December 31, 2016, the Company's obligation under the deferred compensation plan was $23.4 million and $21.7 million, respectively. Employees have the option to transfer balances allocated to their accounts in the defined contribution retirement savings plan and the deferred compensation plan into any of the available investment options.

In connection with the December 14, 2012 acquisition of EECOL, the Company assumed a contributory defined benefit plan covering substantially all Canadian employees of EECOL and a Supplemental Executive Retirement Plan for certain executives of EECOL.

The following table reflects the components of net periodic benefit costs for the defined benefit plans:



	Three Months Ended						Nine Months Ended
	September 30,						September 30,
(In thousands of dollars)	2017			2016			2017			2016
Service cost	$	1,118		$	977		$	3,234		$	2,889
Interest cost	1,007			979			2,915			2,898
Expected return on plan assets	(1,432		)	(1,353		)	(4,144		)	(4,004		)
Recognized actuarial gain	(51		)	(10		)	(149		)	(31		)
Net periodic benefit cost	$	642		$	593		$	1,856		$	1,752

During the three and nine months ended September 30, 2017, there were no employer contributions to the defined benefit plans. During the three and nine months ended September 30, 2016, the Company made aggregate cash contributions of $0.5 million and $1.4 million, respectively, to the defined benefit plans.