12. Earnings per share of QTS Realty Trust, Inc.

Basic income per share is calculated by dividing the net income attributable to common shares by the weighted average number of common shares outstanding during the period. Diluted income per share adjusts basic income per share for the effects of potentially dilutive common shares. Unvested restricted stock awards contain non-forfeitable rights to dividends and thus are participating securities and are included in the computation of earnings per share pursuant to the two-class method for all periods presented. The two-class method is an earnings allocation formula that treats a participating security as having rights to undistributed earnings that would otherwise have been available to common stockholders. Accordingly, service-based restricted stock awards were included in the calculation of earnings per share using the two-class method for all periods presented.

The computation of basic and diluted net income per share is as follows (in thousands, except per share data):


	Year Ended
	December 31,
	2017		2016		2015
Numerator:
Net income available to common stockholders - basic	$	1,282	$	21,525	$	20,326
Effect of net income attributable to noncontrolling interests and income allocated to participating securities		(593)		3,160		3,803
Net income available to common stockholders	$	689	$	24,685	$	24,129
Denominator:
Weighted average shares outstanding - basic		48,381		46,206		37,568
Effect of Class A and Class RS partnership units *		6,696		6,783		7,029
Effect of Class O units and options to purchase Class A common stock and restricted Class A common stock on an "as if" converted basis *		779		973		756
Weighted average shares outstanding - diluted		55,856		53,962		45,353

Basic net income per share	$	0.01	$	0.47	$	0.54

Diluted net income per share	$	0.01	$	0.46	$	0.53

The Class A units and Class O units represent limited partnership interests in the Operating Partnership, and are described in more detail in Note 8

No securities were antidilutive for the years ended December 31, 2017, 2016 and 2015, and as such, no securities were excluded from the computation of diluted net income per share for those periods.