23. Earnings Per Share

The following table reconciles the basic to diluted weighted average shares outstanding (in millions):

	Year Ended December 31,
	2017		2016		2015
Basic weighted average common shares outstanding		217.8		149.1		123.0
Effect of dilutive stock options and share awards		4.8		2.9		2.6
Diluted weighted average common shares outstanding		222.6		152.0		125.6

The following table presents the weighted average number of outstanding stock-based awards not included in the computation of diluted earnings per share if they are subject to performance conditions or if the effect of including such stock-based awards in the computation would be anti-dilutive (in millions):

	Year Ended December 31,
	2017		2016		2015
Shares subject to performance conditions		0.4		0.1		0.1
Shares subject to anti-dilutive stock-based awards		1.0		1.1		1.0
Total shares excluded from diluted earnings per share		1.4		1.2		1.1

The vesting of performance awards is contingent upon the achievement of certain performance targets. The performance awards are not included in diluted earnings per share until the performance targets have been met.

Stock-based awards will have a dilutive effect under the treasury method when the respective period’s average market value of the Company’s common stock exceeds the exercise proceeds.