9. Income per Unit

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




	Year Ended December 31,
	2012	2011	2010

Net income available to common unitholders	$ 177,819	$ 137,053	$ 61,745

Weighted average units outstanding--basic	119,861,380	103,053,004	89,261,172
Potentially dilutive common units:
Stock options	72,818	187,834	201,704
Class C Units (2007 Grant)	-	15,050	97,761
Unvested incentive units	216,092	190,771	186,691
Excess exchange value of the 2026 Debentures	-	370,719	1,251,817
Weighted average units outstanding--diluted	120,150,290	103,817,378	90,999,145
Income per unit:
Basic	$ 1.48	$ 1.33	$ 0.69
Diluted	$ 1.48	$ 1.32	$ 0.68

During the year ended December 31, 2011, the remaining 2026 Debentures were redeemed and exchanged. 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. Using the treasury method, 370,719 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 year ended December 31, 2011. During the year ended December 31, 2010, the weighted average common stock price exceeded the strike price of $31.42 per share. Therefore, using the treasury method, 1,251,817 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 year ended December 31, 2010.

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



	Year Ended December 31,
	2012	2011	2010

Potentially dilutive 2029 Debentures	6,486,358	6,328,234	6,217,841
Potentially dilutive Series C Cumulative Convertible Preferred Units	814,063	3,016,780	3,671,190
Potentially dilutive Series D Cumulative Convertible Preferred Units	4,016,560	6,242,257	8,271,022
Potentially dilutive Series E Cumulative Redeemable Preferred Units	4,122,752	1,311,310	-
Potentially dilutive Series F Cumulative Redeemable Preferred Units	1,304,940	-	-
	16,744,673	16,898,581	18,160,053