Net Income Per Share

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 September 30		Nine months ended September 30
	2017	2016	2017	2016
	(in thousands)
Weighted average shares outstanding (basic)	174,991	173,020	174,582	173,248
Impact of common stock equivalents	1,225	1,044	1,194	1,017
Weighted average shares outstanding (diluted)	176,216	174,064	175,776	174,265

For the three and nine months ended September 30, 2016, 447,000 and 712,000 stock options, respectively, were excluded from the diluted net income per share computation as their effect would have been anti-dilutive. There were no stock options excluded for the three and nine months ended September 30, 2017.