8. Income per Unit

The following is a summary of basic and diluted income per unit (in thousands, except unit and per unit amounts):


	Three Months Ended March 31,
	2012		2011
Net income available to common unitholders	$	40,797	$	32,632

Weighted average units outstanding—basic		111,432,822		96,302,608
Potentially dilutive common units:
Stock options		205,830		202,038
Class C Units (2007 Grant)		16,358		92,795
Unvested incentive units		262,812		153,066
Excess exchange value of the 2026 Debentures		—		723,961

Weighted average units outstanding—diluted		111,917,822		97,474,468

Income per unit:
Basic	$	0.37	$	0.34

Diluted	$	0.36	$	0.33

On or after July 15, 2026, the 2026 Debentures would have been exchangeable at the then-applicable exchange rate for cash (up to the principal amount of the 2026 Debentures) and, with respect to any excess exchange value, into cash, shares of Digital Realty Trust, Inc. common stock or a combination of cash and shares of Digital Realty Trust, Inc. common stock. Pursuant to the terms of the Operating Partnership's agreement of limited partnership, the Operating Partnership would have delivered to Digital Realty Trust, Inc. one common unit for each share of common stock issued upon exchange of the 2026 Debentures. The 2026 Debentures also would have been exchangeable prior to July 15, 2026, but only upon the occurrence of certain specified events, including if the weighted average common stock price exceeded a specified strike price as of the end of a fiscal quarter. During the year ended December 31, 2011, the remaining 2026 Debentures were redeemed and exchanged. Using the treasury method, 723,961 common units contingently issuable upon settlement of the excess exchange value were included as potentially dilutive common units in determining diluted earnings per unit for the three months ended March 31, 2011.

We have excluded the following potentially dilutive securities in the calculations above as they would be antidilutive or not dilutive:


	Three Months Ended March 31,
	2012		2011
Potentially dilutive 2029 Debentures		6,442,085		6,269,990
Potentially dilutive Series C Cumulative Convertible Preferred Units		2,784,845		3,652,324
Potentially dilutive Series D Cumulative Convertible Preferred Units		4,337,429		8,333,421
Potentially dilutive Series E Cumulative Redeemable Preferred Units		4,025,863		—

		17,590,222		18,255,735