(7) Earnings Per Share Data (“EPS”) and Stock Based Compensation

Basic earnings per share are based on the weighted average number of common shares outstanding during the period. Diluted earnings per share are based on the weighted average number of common shares outstanding during the period adjusted to give effect to common stock equivalents.

The following table sets forth the computation of basic and diluted earnings per share for classes A, B, C and D common stockholders for the periods indicated (in thousands, except per share data):

	Three months ended March 31,
	2018			2017
Basic and Diluted:
Net income attributable to UHS	$	223,832		$	206,055
Less: Net income attributable to unvested restricted share grants		(104	)		(94	)
Net income attributable to UHS – basic and diluted	$	223,728		$	205,961

Weighted average number of common shares - basic		94,226			96,585
Net effect of dilutive stock options and grants based on the treasury stock method		457			787
Weighted average number of common shares and equivalents - diluted		94,683			97,372
Earnings per basic share attributable to UHS:	$	2.37		$	2.13
Earnings per diluted share attributable to UHS:	$	2.36		$	2.12

The “Net effect of dilutive stock options and grants based on the treasury stock method”, for all periods presented above, excludes certain outstanding stock options applicable to each period since the effect would have been anti-dilutive. The excluded weighted-average stock options totaled 2.9 million for the three months ended March 31, 2018. The excluded weighted-average stock options totaled 5.7 million for the three months ended March 31, 2017. All classes of our common stock have the same dividend rights.

Stock-Based Compensation:

During the three-month periods ended March 31, 2018 and 2017, pre-tax compensation cost of $18.9 million and $14.9 million, respectively, was recognized related to outstanding stock options. In addition, during the three-month periods ended March 31, 2018 and 2017, pre-tax compensation cost of approximately $545,000 and $150,000 (net of cancellations), respectively, was recognized related to restricted stock. As of March 31, 2018 there was approximately $87.0 million of unrecognized compensation cost related to unvested options and restricted stock which is expected to be recognized over the remaining weighted average vesting period of 2.4 years. There were 4,000 stock options granted during the first three months of 2018 with a weighted-average grant date fair value of $29.6425 per share. There were 16,926 shares of restricted shares granted during the first three months of 2018 with a weighted-average grant date fair value of $117.98 per share.

The expense associated with stock-based compensation arrangements is a non-cash charge. In the Condensed Consolidated Statements of Cash Flows, stock-based compensation expense is an adjustment to reconcile net income to cash provided by operating activities and aggregated to $19.7 million and $15.3 million during the three-month periods ended March 31, 2018 and 2017, respectively.