Per Share Information

12 Months Ended

Dec. 31, 2019

PER SHARE INFORMATION:

The amounts used to compute basic and diluted earnings per share attributable to common stock for the years ended December 31, 2019, 2018 and 2017 consisted of the following (in thousands):



	Year Ended December 31,
	2019		2018		2017
Amounts attributable to common stock:
Net income attributable to common stock	$	402,044	$	293,346	$	314,978
Weighted average shares:
Weighted average shares outstanding for basic earnings per share attributable to common stock	145,710		152,963		156,124
Effect of dilutive unvested non-participating stock-based awards	1,824		1,263		1,031
Weighted average shares outstanding for diluted earnings per share attributable to common stock	147,534		154,226		157,155

Basic and diluted earnings per share attributable to common stock are computed using the weighted average number of shares of common stock outstanding during the applicable period. Exchangeable shares that were issued pursuant to certain of Quanta’s historical acquisitions (as further discussed in Note 11), which are exchangeable on a one-for-one basis with shares of Quanta common stock, have been included in the calculation of weighted average shares outstanding for basic and diluted earnings per share attributable to common stock for the portion of the periods that they were outstanding. Additionally, unvested stock-based awards that contain non-forfeitable rights to dividends or dividend equivalents (participating securities) have been included in the calculation of basic and diluted earnings per share attributable to common stock for the portion of the periods that the awards were outstanding. Weighted average shares outstanding for basic and diluted earnings per share attributable to common stock for the years ended December 31, 2019, 2018 and 2017 included 2.8 million, 2.6 million and 2.3 million weighted average participating securities.

For purposes of calculating diluted earnings per share attributable to common stock, there were no adjustments required to derive Quanta’s net income attributable to common stock. Diluted earnings per share attributable to common stock is computed using the weighted average number of shares of common stock outstanding during the period adjusted for all potentially dilutive common stock equivalents, except in cases where the effect of the common stock equivalents would be antidilutive.