21. Earnings Per Share

The computations of basic and diluted net earnings per share are as follows (in thousands, except per share data):


Year Ended December 31,	2017			2016			2015
Basic net earnings per share:
Basic net earnings	$	1,318,688		$	796,271		$	80,724
Earnings allocated to participating securities		(4,549	)		(2,632	)		(1,514	)

Net earnings available to common stockholders	$	1,314,139		$	793,639		$	79,210

Average shares outstanding		319,990			319,563			320,565

Basic net earnings per share	$	4.11		$	2.48		$	0.25

Diluted net earnings per share:
Diluted net earnings	$	1,318,688		$	796,271		$	80,724
Earnings allocated to participating securities		(4,539	)		(2,631	)		(1,514	)

Net earnings available to common stockholders	$	1,314,149		$	793,640		$	79,210

Diluted average shares outstanding:
Basic shares outstanding		319,990			319,563			320,565
Dilutive effect of stock options and other		783			259			114

		320,773			319,822			320,679

Diluted net earnings per share	$	4.10		$	2.48		$	0.25

The following stock options were excluded from the computation of diluted net earnings per share because their effect would have been anti-dilutive (shares in thousands):


Year Ended December 31,	2017		2016		2015
Anti-dilutive stock options:
Weighted-average shares		407		942		1,226

Weighted-average exercise price	$	59.07	$	47.04	$	47.20