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

Our common stock and common partnership unit equivalents include options to purchase shares of Common Stock, which, if exercised, would result in Aimco’s issuance of additional shares and the Aimco Operating Partnership’s issuance to Aimco of additional common partnership units equal to the number of shares purchased under the options. These equivalents also include

unvested total shareholder return, or TSR, 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 common partnership units outstanding equal to the number of shares that vest. Common partnership unit equivalents also include unvested long-term incentive partnership units. We include in the denominator securities with dilutive effect in calculating diluted earnings per share and per unit during these periods.

Our restricted stock awards that are subject to time-based vesting receive non-forfeitable dividends similar to shares of Common Stock and common partnership units prior to vesting, and our TSR long-term incentive partnership units receive non-forfeitable distributions based on specified percentages of the distributions paid to common partnership 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.

Reconciliations of the numerator and denominator in the calculations of basic and diluted earnings per share and per unit for the three and six months ended June 30, 2020 and 2019, are as follows (in thousands, except per share and per unit data):

	Three Months Ended June 30,				Six Months Ended June 30,
	2020		2019		2020		2019
Earnings per share
Numerator:
Basic and dilutive net income attributable to Aimco common stockholders	$	39,212	$	59,234	$	45,891	$	330,802

Denominator – shares:
Basic weighted-average Common Stock outstanding		148,535		148,367		148,527		146,994
Dilutive share equivalents outstanding		18		232		143		226
Dilutive weighted-average Common Stock outstanding		148,553		148,599		148,670		147,220

Earnings per share – basic and diluted	$	0.26	$	0.40	$	0.31	$	2.25

Non-dilutive share equivalents outstanding		8,929		—		8,260		—

Earnings per unit
Numerator:
Basic and dilutive net income attributable to the Aimco Operating Partnership's common unitholders	$	41,319	$	62,817	$	48,366	$	349,456

Denominator – units
Basic weighted-average common partnership units outstanding		156,509		156,637		156,584		155,158
Dilutive partnership unit equivalents outstanding		18		381		218		359
Dilutive weighted-average common partnership units outstanding		156,527		157,018		156,802		155,517

Earnings per unit – basic and diluted	$	0.26	$	0.40	$	0.31	$	2.25

Non-dilutive partnership unit equivalents outstanding		2,081		—		1,214		—

The Aimco Operating Partnership has various classes of preferred OP Units, which may be redeemed at the holders’ option. The Aimco Operating Partnership may redeem these units for cash, or at its option, shares of Common Stock. As of June 30, 2020, these preferred OP Units were potentially redeemable for approximately 2.6 million shares of Common Stock (based on the period end market price), or cash. The Aimco Operating Partnership has a redemption policy that requires cash settlement of redemption requests for the preferred OP Units, subject to limited exceptions. Accordingly, we have excluded these securities from earnings per share and unit computations for the periods presented above, and we expect to exclude them in future periods.

During the three and six months ended June 30, 2020, we paid $0.41 and $0.82, respectively, in dividends and distributions per share and per unit. During the three and six months ended June 30, 2019, we paid $0.39 and $2.41, respectively, in dividends and distributions per share and per unit. Of the $2.41 paid in dividends and distributions in 2019, $2.02 represents the per share and per unit value of the special dividend and special distribution authorized by the Board of Directors in the first quarter of 2019. The special dividend consisted of $67.1 million in cash, 4.5 million shares of Common Stock, and $0.4 million of cash paid in lieu of issuing fractional shares. The special distribution consisted of $72.7 million in cash, 4.8 million common partnership units, and $0.4 million of cash paid in lieu of issuing fractional units.