4.	Real Estate

Investments in real estate properties are presented at cost, and consist of the following as of December 31 (square feet and dollars in thousands):


	Square Feet /Acres (1)				No. of Buildings (1)				Investment Balance
	2013		2012		2013		2012		2013		2012
Industrial operating properties:
Improved land		- -		- -		- -		- -	$	4,074,647	$	5,317,123
Buildings and improvements		267,097		316,347		1,610		1,853		13,726,417		17,291,125
Development portfolio, including cost of land:
Pre-stabilized		4,491		4,785		11		15		204,022		472,413
Properties under development		18,587		13,216		46		30		816,995		479,230
Land		9,747		10,915		- -		- -		1,516,166		1,794,364
Other real estate investments (2)		- -		- -		- -		- -		486,230		454,868

Total investments in real estate properties										20,824,477		25,809,123
Less accumulated depreciation										2,568,998		2,480,660

Net investments in real estate properties									$	18,255,479	$	23,328,463

(1)	Items indicated by ‘ - - ‘ are not applicable.

(2)

Included in other investments were: (i) certain non-industrial real estate; (ii) our corporate office buildings; (iii) land parcels that are ground leased to third parties; (iv) certain infrastructure costs related to projects we are developing on behalf of others; (v) costs related to future development projects, including purchase options on land; (vi) earnest money deposits associated with potential acquisitions; and (vii) restricted funds that are held in escrow pending the completion of tax-deferred exchange transactions involving operating properties.

At December 31, 2013, excluding our assets held for sale, we owned real estate assets in the Americas (Canada, Mexico and the United States), Europe (Austria, Belgium, the Czech Republic, France, Germany, Hungary, Italy, the Netherlands, Poland, Romania, Slovakia, Spain, Sweden and the United Kingdom) and Asia (China, Japan, and Singapore).

Acquisitions

Real estate acquisition activity for the years ended December 31, 2013, 2012 and 2011 was as follows (dollars and square feet in thousands):


	2013		2012		2011
Acquisitions of properties from unconsolidated co-investment ventures
Number of properties		58		215		233
Square feet		16,319		46,277		53,603
Real estate acquisition value	$	1,141,128	$	2,294,892	$	4,591,017
Net gains	$	34,787	$	286,335	$	99,369

Building acquisitions from third parties
Number of properties		12		12		8
Square feet		3,262		1,622		1,498
Real estate acquisition value	$	146,331	$	77,397	$	86,851

The acquisitions of properties from unconsolidated co-investment ventures primarily relate to when we have acquired all or a portion of the third parties share of a co-investment venture upon dissolution of the venture.

Dispositions

Real estate disposition activity for the years ended December 31, 2013, 2012 and 2011 was as follows (dollars and square feet in thousands):


	2013		2012		2011
Continuing Operations
Number of properties		254		25		57
Square feet		71,503		4,784		7,784
Net proceeds from contributions and dispositions	$	6,656,980	$	475,467	$	731,072
Net gains from contributions and dispositions	$	562,869	$	19,272	$	12,315

Discontinued Operations
Number of properties		89		200		94
Square feet		9,196		27,169		10,739
Net proceeds from dispositions	$	608,286	$	1,562,189	$	931,443
Net gains from dispositions, including related impairment charges and taxes	$	116,550	$	35,098	$	58,614

Lease Commitments

We have entered into operating ground leases as a lessee on certain land parcels, primarily on-tarmac facilities and office space with remaining lease terms of 1 to 75 years. Buildings and improvements subject to ground leases are depreciated ratably over the shorter of the term of the related leases or the useful life of the real estate. Future minimum rental payments under non-cancelable operating leases in effect as of December 31, 2013, were as follows (in thousands):


2014	$	36,474
2015		34,105
2016		25,434
2017		22,956
2018		20,752
Thereafter		227,141

Total	$	366,862

Operating Lease Agreements

We lease our operating properties and certain land parcels to customers under agreements that are generally classified as operating leases. Our largest customer and 25 largest customers accounted for 1.6% and 22.6%, respectively, of our annualized base rents at December 31, 2013. At December 31, 2013, minimum lease payments on leases with lease periods greater than one year for space in our operating properties and leases of land subject to ground leases were as follows (in thousands):


2014	$	1,106,254
2015		966,365
2016		780,354
2017		574,171
2018		421,255
Thereafter		1,139,570

Total	$	4,987,969

These amounts do not reflect future rental revenues from the renewal or replacement of existing leases and exclude reimbursements of operating expenses. These reimbursements are reflected as rental recoveries and rental expenses in the accompanying Consolidated Statements of Operations.