Aimco and Aimco Operating Partnership calculate basic earnings per share and basic earnings per unit based on the weighted-average number of shares of Common Stock and OP Units outstanding. We calculate diluted earnings per share and diluted earnings per unit taking into consideration dilutive shares of Common Stock and OP Unit equivalents and dilutive convertible securities outstanding during the period.

Aimco's Common Stock and OP Unit equivalents include options to purchase shares of Common Stock, which, if exercised, would result in Aimco's issuance of additional shares of Common Stock and Aimco Operating Partnership’s issuance to Aimco of additional OP Units equal to the number of shares of Common Stock purchased under the options. These equivalents also include unvested market-based restricted stock awards that do not meet the definition of participating securities, which would result in an increase in the number of shares of Common Stock and OP Units outstanding equal to the number of the shares that vest. OP Unit equivalents also include unvested long-term incentive partnership units. The Common Stock and OP Unit equivalents were not included in the computation of diluted earnings per share and unit for the years ended December 31, 2021 and December 31, 2023, because the effect of their inclusion would be antidilutive. The Common Stock and OP Unit equivalents were included in the computation of diluted earnings per share and unit for the year ended December 31, 2022, because the effect of their inclusion was dilutive. As of December 31, 2023, the Common Stock and OP Unit equivalents that could potentially dilute basic earnings per share or unit in future periods totaled 3.7 million and 8.0 million, respectively.

Aimco's time-based restricted stock awards receive non-forfeitable dividends similar to shares of Common Stock and OP Units prior to vesting, and our market-based long-term incentive partnership units ("LTIP Units") receive non-forfeitable distributions based on specified percentages of the distributions paid to OP Units prior to vesting and conversion. The unvested restricted shares and units related to these awards are participating securities. We include the effect of participating securities in basic and diluted earnings per share and unit computations using the two-class method of allocating distributed and undistributed earnings when the two-class method is more dilutive than the treasury stock method. Participating securities were not included in the computation of diluted earnings per share and unit for the years ended December 31, 2021 and December 31, 2023, because the effect of their inclusion would be antidilutive. Participating securities were included in the computation of diluted earnings per share and unit for the year ended December 31, 2022, because the effect of their inclusion was dilutive. As of December 31, 2023, participating securities that could potentially dilute basic earnings per share or unit in future periods totaled 2.5 million.

Reconciliations of the numerator and denominator in the calculations of basic and diluted earnings per share and per unit for the years ended December 31, 2023, 2022 and 2021, are as follows (in thousands, except per share and per unit data):


	Year ended December 31,
	2023			2022			2021
Earnings per share
Numerator:
Net income (loss) attributable to Aimco	$	(166,196	)	$	75,726		$	(5,910	)
Net income (loss) allocated to Aimco participating securities		—			(1,087	)		—
Net income (loss) attributable to Aimco common stockholders	$	(166,196	)	$	74,639		$	(5,910	)

Denominator - shares:
Basic weighted-average common stock outstanding		143,618			149,395			149,480
Diluted share equivalents outstanding		—			1,439			—
Diluted weighted-average common stock outstanding		143,618			150,834			149,480

Earnings (loss) per share - basic	$	(1.16	)	$	0.50		$	(0.04	)
Earnings (loss) per share - diluted	$	(1.16	)	$	0.49		$	(0.04	)

Earnings per unit
Numerator:
Net income (loss) attributable to Aimco Operating Partnership	$	(175,234	)	$	79,657		$	(6,207	)
Net income (loss) allocated to Aimco Operating Partnership participating securities		—			(1,131	)		—
Net income (loss) attributable to Aimco Operating Partnership's common unit holders	$	(175,234	)	$	78,526		$	(6,207	)

Denominator - units
Basic weighted-average OP Units outstanding		151,371			157,317			157,701
Diluted OP Unit equivalents outstanding		—			1,457			-
Diluted weighted-average OP Units outstanding		151,371			158,774			157,701

Earnings (loss) per unit - basic	$	(1.16	)	$	0.50		$	(0.04	)
Earnings (loss) per unit - diluted	$	(1.16	)	$	0.49		$	(0.04	)