13. Earnings per Share

Basic earnings per share of Class A common stock is calculated by dividing the net income attributable to Cactus Inc. during the period by the weighted average number of shares of Class A common stock outstanding during the same period. Diluted earnings per share of Class A common stock is calculated by dividing the net income attributable to Cactus Inc. during that period by the weighted average number of common shares outstanding assuming all potentially dilutive shares were issued.

The Company uses the “if-converted” method to determine the potential dilutive effect of outstanding CW Units (and corresponding shares of its outstanding Class B common stock), and the treasury stock method to determine the potential dilutive effect of unvested restricted stock units assuming that the proceeds will be used to purchase shares of Class A common stock.

There were no shares of Class A common stock or Class B common stock outstanding prior to February 12, 2018, therefore no earnings per share information has been presented for any period prior to that date.

The following table summarizes the basic and diluted earnings per share calculations (shares in thousands):


	Three Months Ended March 31,
	2019		2018
Numerator:
Net income attributable to Cactus Inc. (1)	$	26,807	$	3,753
Denominator:
Weighted average Class A shares outstanding—basic		38,719		26,450
Effect of dilutive shares (2)		36,527		198
Weighted average Class A shares outstanding—diluted (2)		75,246		26,648

Earnings per Class A share—basic	$	0.69	$	0.14
Earnings per Class A share—diluted (1) (2)	$	0.59	$	0.14

(1)

Under the if-converted method, the numerator is adjusted in the calculation of diluted earnings per share to include $17.5 million of additional income attributable to non-controlling interest adjusted for a corporate effective tax rate of 24%.

(2)

Diluted earnings per share for the three months ended March 31, 2019 includes 36,292 shares of Class B common stock assuming conversion, plus the dilutive effect of 235 shares of restricted stock unit awards. Diluted earnings per share for the three months ended March 31, 2018 excludes 48,440 shares of Class B common stock as the effect would be anti-dilutive.