Net Income Per Share

3 Months Ended

Mar. 31, 2018

Basic net income per share is calculated as net income divided by the weighted average number of shares outstanding. Diluted net income per share is calculated as net income divided by the weighted average number of shares outstanding plus the incremental number of shares added as a result of converting common stock equivalents, calculated using the treasury stock method. The Corporation’s common stock equivalents consist of outstanding stock options, restricted stock units ("RSUs") and performance-based restricted stock units ("PSUs"). PSUs are required to be included in weighted average shares outstanding if performance measures, as defined in each PSU award agreement, are met as of the end of the period.

A reconciliation of weighted average shares outstanding used to calculate basic net income per share and diluted net income per share follows:



	Three months ended March 31
	2018	2017
	(in thousands)
Weighted average shares outstanding (basic)	175,303	174,150
Impact of common stock equivalents	1,265	1,427
Weighted average shares outstanding (diluted)	176,568	175,577