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•	enhances investors' understanding of the General Partner and the Partnership by enabling investors to view the business as a whole in the same manner as management views and operates the business;

•	eliminates duplicative disclosure and provides a more streamlined and readable presentation of information since a substantial portion of the Company's disclosure applies to both the General Partner and the Partnership; and

•	creates time and cost efficiencies through the preparation of one combined report instead of two separate reports.

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•	Changes in general economic and business conditions, including the financial condition of our tenants and the value of our real estate assets;

•	The General Partner's continued qualification as a real estate investment trust ("REIT") for U.S. federal income tax purposes;

•	Heightened competition for tenants and potential decreases in property occupancy;

•	Potential changes in the financial markets and interest rates;

•	Volatility in the General Partner's stock price and trading volume;

•	Our continuing ability to raise funds on favorable terms;

•	Our ability to successfully identify, acquire, develop and/or manage properties on terms that are favorable to us;

•	Potential increases in real estate construction costs;

•	Our ability to successfully dispose of properties on terms that are favorable to us, including, without limitation, through one or more transactions that are consistent with our previously disclosed strategic plans;

•	Our ability to retain our current credit ratings;

•	Inherent risks in the real estate business, including, but not limited to, tenant defaults, potential liability relating to environmental matters and liquidity of real estate investments; and

•	Other risks and uncertainties described herein, as well as those risks and uncertainties discussed from time to time in our other reports and other public filings with the Securities and Exchange Commission ("SEC").

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•	We could become engaged in a dispute with any of our joint venture partners that might affect our ability to develop or operate a property;

•	Our joint venture partners may have different objectives than we have regarding the appropriate timing and terms of any sale or refinancing of properties;

•	Our joint venture partners may have competing interests in our markets that could create conflict of interest issues; and

•	Maturities of debt encumbering our jointly owned investments may not be able to be refinanced at all or on terms that are as favorable as the current terms.

•	Changes in the general economic climate;

•	The availability of capital on favorable terms, or at all;

•	Increases in interest rates;

•	Local conditions such as oversupply of property or a reduction in demand;

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•	Competition for tenants;

•	Changes in market rental rates;

•	Oversupply or reduced demand for space in the areas where our properties are located;

•	Delay or inability to collect rent from tenants who are bankrupt, insolvent or otherwise unwilling or unable to pay;

•	Difficulty in leasing or re-leasing space quickly or on favorable terms;

•	Costs associated with periodically renovating, repairing and reletting rental space;

•	Our ability to provide adequate maintenance and insurance on our properties;

•	Our ability to control variable operating costs;

•	Changes in government regulations; and

•	Potential liability under, and changes in, environmental, zoning, tax and other laws.

•	Unsuccessful development opportunities could result in direct expenses to us;

•	Construction costs of a project may exceed original estimates, possibly making the project less profitable than originally estimated, or possibly unprofitable;

•	Time required to complete the construction of a project or to lease up the completed project may be greater than originally anticipated, thereby adversely affecting our cash flow and liquidity;

•	Occupancy rates and rents of a completed project may not be sufficient to make the project profitable; and

•	Favorable sources to fund our development activities may not be available.

•	Prices paid for acquired facilities are based upon a series of market judgments; and

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•	Costs of any improvements required to bring an acquired facility up to standards to establish the market position intended for that facility might exceed budgeted costs.

•	liabilities for clean-up of undisclosed environmental contamination;

•	claims by tenants, vendors or other persons against the former owners of the properties;

•	liabilities incurred in the ordinary course of business; and

•	claims for indemnification by general partners, directors, officers and others indemnified by the former owners of the properties.

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•	The General Partner would not be allowed a deduction for distributions to shareholders and would be subject to federal income tax (including any applicable alternative minimum tax) on its taxable income at regular corporate rates;

•	Unless the General Partner was entitled to relief under certain statutory provisions, it would be disqualified from treatment as a REIT for the four taxable years following the year during which it ceased to qualify as a REIT;

•	The General Partner's net earnings available for investment or distribution to its shareholders would decrease due to the additional tax liability for the year or years involved; and

•	The General Partner would no longer be required to make any distributions to shareholders in order to qualify as a REIT.

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•	The holders of 80% of the General Partner's outstanding shares of capital stock approve the transaction;

•	The transaction has been approved by three-fourths of those directors who served on the General Partner's board before the shareholder became a 10% owner; or

•	The significant shareholder complies with the "fair price" provisions of the General Partner's charter.

•	Any voluntary sale, exchange, merger, consolidation or other disposition of all or substantially all of the assets of the Partnership in one or more transactions other than a disposition occurring upon a financing or refinancing of the Partnership;

•	The General Partner's merger, consolidation or other business combination with another entity unless after the transaction substantially all of the assets of the surviving entity are contributed to the Partnership in exchange for Common Units;

•	The General Partner's assignment of its interests in the Partnership other than to one of its wholly-owned subsidiaries; and

•	Any reclassification or recapitalization or change of outstanding shares of the General Partner's common stock other than certain changes in par value, stock splits, stock dividends or combinations.

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(1)	Represents the average annual base rental payments, on a straight-line basis for the term of each lease, from space leased to tenants as of December 31, 2012, excluding additional amounts paid by tenants as reimbursement for operating expenses. Joint venture properties are shown at 100% of square feet and net effective rents, without regard to our ownership percentage.

(2)	Annual net effective rent per leased square foot.

(3)	Represents properties not located in our primary markets, totaling 2.7% of the total square footage of our consolidated properties.

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•

Owned or jointly controlled 774 industrial, office, medical office and other properties, of which 755 properties with approximately 141.2 million square feet are in service and 19 properties with more than 4.4 million square feet are under development. The 755 in-service properties are comprised of 629 consolidated properties with approximately 115.6 million square feet and 126 jointly controlled properties with more than 25.6 million square feet. The 19 properties under development consist of 17 consolidated properties with approximately 3.6 million square feet and two jointly controlled properties with approximately 874,000 square feet.

•	Owned, including through ownership interests in unconsolidated joint ventures, more than 4,600 acres of land and controlled an additional 1,600 acres through purchase options.

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•	During 2012, we acquired 27 medical office properties and ten industrial properties with a total combined value of $779.7 million.

•	We generated $138.1 million of total net cash proceeds from the disposition of 28 wholly-owned buildings and 210 acres of wholly-owned undeveloped land.

•	We had development starts of $485.2 million within our consolidated properties, which were primarily comprised of industrial and medical office properties. These 2012 development starts were 86% pre-leased.

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We increased our level of development investment during 2012 as compared to the last few years. The total estimated cost of our consolidated properties under construction was $468.8 million at December 31, 2012, with $225.2 million of such costs incurred through that date. The total estimated cost for jointly controlled properties under construction was $109.6 million at December 31, 2012, with $55.0 million of costs incurred through that date. The consolidated properties under construction are 84% pre-leased, while the jointly controlled properties under construction are 31% pre-leased.

•	The occupancy level for our in-service portfolio of consolidated properties increased from 90.8% at December 31, 2011 to 92.7% at December 31, 2012. The increase in occupancy was primarily driven by leasing up vacant space, as well as our acquisition and disposition activities.

•	We continued to have strong total leasing activity for our consolidated properties, with total leasing activity of 24.2 million square feet in 2012 compared to 19.7 million square feet in 2011.

•	Total leasing activity for our consolidated properties in 2012 included 13.6 million square feet of renewals, which represented an 83.7% retention rate, on a square foot basis, and resulted in a 1.4% increase in net effective rents.

•	In January 2013, the General Partner completed a public offering of 41.4 million common shares, at an issue price of $14.25 per share, resulting in gross proceeds of $590.0 million and, after underwriting fees

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•	Throughout 2012, the General Partner issued 22.7 million shares of common stock pursuant to its at the market ("ATM") equity program, generating gross proceeds of approximately $322.2 million and, after considering commissions and other costs, net proceeds of approximately $315.3 million.

•	In October 2012, we repaid $50.0 million of medium term notes, which had an effective interest rate of 5.45%, at their scheduled maturity date.

•	In September 2012, we issued $300.0 million of unsecured notes that bear interest at 3.875%, have an effective rate of 3.925%, and mature on October 15, 2022.

•	In August 2012, we repaid $150.0 million of senior unsecured notes, which had an effective interest rate of 6.01%, at their scheduled maturity date.

•	In June 2012, we issued $300.0 million of senior unsecured notes that bear interest at 4.375%, have an effective rate of 4.466%, and mature on June 15, 2022.

•	In March 2012, the General Partner redeemed all of the outstanding shares of its 6.950% Series M Cumulative Redeemable Preferred Shares ("Series M Shares") at a liquidation amount of $168.3 million.

•	We assumed nine secured loans in conjunction with our 2012 acquisitions. These assumed loans had a total face value of $96.1 million, a total fair value of $100.8 million and carry a weighted average stated interest rate of 5.56%. We used a weighted average estimated market rate of 3.50% in determining the fair value of these loans.

•	Throughout 2012, we repaid five secured loans at their respective maturity dates totaling $102.1 million. These loans had a weighted average stated interest rate of 6.08%.

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•	We acquired 96 properties, of which 51 were industrial and 38 were medical office, and placed eleven developments in service from January 1, 2011 to December 31, 2012, which provided incremental revenues of $91.3 million in the year ended December 31, 2012 over 2011.

•	The sale of 13 office properties to an unconsolidated joint venture in the first quarter of 2011 resulted in a $10.1 million decrease in rental and related revenue from continuing operations in 2012, which partially offset the impact of newly acquired or developed properties.

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The remaining increase in rental and related revenue from continuing operations is primarily due to improved results within the properties that have been in service for all of 2011 and 2012. Higher levels of occupancy primarily drove the overall improvement within these properties, as rental rates increased modestly but did not significantly contribute to the increase in revenues from continuing operations.

•	The overall shift of revenues and income from office properties to industrial and medical office properties is consistent with our continuing strategy to increase our asset concentration in industrial and medical office properties while reducing our overall investment in office properties.

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•	We acquired 108 properties, of which 87 were industrial, and placed nine developments in service from January 1, 2010 to December 31, 2011, which provided incremental revenues of $79.8 million in the year ended December 31, 2011 over 2010.

•	We consolidated 106 industrial buildings as a result of acquiring our joint venture partner's 50% interest in Dugan Realty, L.L.C. ("Dugan") on July 1, 2010. The consolidation of these buildings resulted in an increase of $37.2 million in rental and related revenue for the year ended December 31, 2011, as compared to the same period in 2010.

•	We sold 23 office properties to an unconsolidated joint venture in 2010 and the first quarter of 2011, resulting in a $55.2 million decrease in rental and related revenue from continuing operations in 2011.

•	The remaining increase in rental and related revenues is primarily due to improved results within the properties that have been in service for all of 2010 and 2011. Although rental rates declined slightly on our lease renewals, the effect was not significant to revenues and improved occupancy drove the overall improvement within these properties.

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•	In 2011, we recognized $12.9 million of impairment charges related to parcels of land, which we intend to sell, where recent market activity led us to determine that a decline in fair value had occurred.

•	In 2010, we sold approximately 60 acres of land, in two separate transactions, which resulted in impairment charges of $9.8 million. These sales were opportunistic in nature and we had not identified or actively marketed this land for disposition, as it was previously intended to be held for development.

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The value allocable to the above or below market component of an acquired in-place lease is determined based upon the present value (using a discount rate which reflects the risks associated with the acquired leases) of the difference between (i) the contractual amounts to be received pursuant to the lease over its remaining term and (ii) management's estimate of the amounts that would be received using fair market rates over the remaining term of the lease. The amounts allocated to above market leases are included in deferred leasing and other costs in the balance sheet and below market leases are included in other liabilities in the balance sheet; both are amortized to rental income over the remaining terms of the respective leases.

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Factors considered in determining the value allocable to in-place leases include estimates, during hypothetical expected lease-up periods, of space that is actually leased at the time of acquisition, of lost rent at market rates, fixed operating costs that will be recovered from tenants, and theoretical leasing commissions required to execute similar leases. These intangible assets are included in deferred leasing and other costs in the balance sheet and are amortized over the remaining term of the existing lease, or the anticipated life of the customer relationship, as applicable.

•	We maintain a tenant "watch list" containing a list of significant tenants for which the payment of receivables and future rent may be at risk. Various factors such as late rent payments, lease or debt instrument defaults, and indications of a deteriorating financial position are considered when determining whether to include a tenant on the watch list.

•	As a matter of policy, we reserve the entire receivable balance, including straight-line rent, of any tenant with an amount outstanding over 90 days.

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•	Straight-line rent receivables for any tenant on the watch list or any other tenant identified as a potential long-term risk, regardless of the status of current rent receivables, are reviewed and reserved as necessary.

•	Criteria for identifying and selecting our critical accounting policies;

•	Methodology in applying our critical accounting policies; and

•	Impact of the critical accounting policies on our financial statements.

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•	property investment;

•	leasing/capital costs;

•	dividends and distributions to shareholders and unitholders;

•	long-term debt maturities;

•	opportunistic repurchases of outstanding debt and preferred stock; and

•	other contractual obligations.

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•	Real estate development costs totaled $264.8 million for the year ended December 31, 2012, compared to $162.1 million and $119.4 million for the years ended December 31, 2011 and 2010, respectively. We have increased our development activities in 2012 for industrial and medical office properties.

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During 2012, we paid cash of $665.5 million for real estate acquisitions, compared to $544.8 million in 2011 and $488.5 million in 2010. In addition, we paid cash of $64.9 million for undeveloped land in 2012, compared to $14.1 million in 2011 and $14.4 million in 2010. The increase in land acquisitions in 2012 is the result of land acquired for specific development projects that commenced shortly after acquisition.

•	Sales of land and depreciated property provided $138.1 million in net proceeds in 2012, compared to $1.57 billion in 2011 and $499.5 million in 2010.

•	We received capital distributions (as a result of the sale of properties or refinancing) from unconsolidated subsidiaries of $5.2 million in 2012, $59.3 million in 2011 and $22.1 million in 2010.

•	During 2012, we contributed or advanced $28.5 million to fund development activities within unconsolidated companies, compared to $34.6 million in 2011 and $53.2 million in 2010.

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•	Throughout 2012, the General Partner issued 22.7 million shares of common stock for net proceeds of $315.3 million. The General Partner had no common stock issuances in 2011. In June 2010, the General Partner issued 26.5 million shares of common stock for net proceeds of $298.1 million.

•	In March 2012, the General Partner redeemed all of the outstanding shares of its Series M Shares for a total payment of $168.3 million. In July 2011, the General Partner redeemed all of the outstanding shares of its Series N Shares for a total payment of $108.6 million.

•	Throughout 2011 and 2010, the General Partner completed open market repurchases of approximately 80,000 shares and 4.5 million shares, respectively, of its Series O Shares. The General Partner paid $2.1 million in 2011 for shares that had a face value of $2.0 million, compared to $118.8 million in 2010 for shares that had a face value of $112.1 million.

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In September 2012, we issued $300.0 million of senior unsecured notes that bear interest at 3.875% and mature on October 15, 2022. In June 2012, we issued $300.0 million of senior unsecured notes that bear interest at 4.375% and mature on June 15, 2022. We had no senior unsecured note issuances in 2011. In April 2010, we issued $250.0 million of senior unsecured notes that bear interest at an effective rate of 6.75% and mature in March 2020.

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In October 2012, we repaid $50.0 million of medium term notes, which had an effective interest rate of 5.45%, at their scheduled maturity date. In August 2012, we repaid $150.0 million of senior unsecured notes, which had an effective interest rate of 6.01%, at their scheduled maturity date. In July 2012, one of our consolidated subsidiaries repaid $21.0 million of variable rate unsecured debt, which bore interest at a rate of LIBOR plus 0.85%, at its scheduled maturity. In December 2011, we repaid the remaining $167.6 million of our 3.75% Exchangeable Notes, which had an effective interest rate of 5.62%, at their scheduled maturity date. In August and March 2011, we also repaid $122.5 million and $42.5 million, respectively, of unsecured notes with an effective rate of 5.69% and 6.96%, respectively, at their scheduled maturity dates. In January 2010, we repaid $99.8 million of senior unsecured notes with an effective interest rate of 5.37% at their scheduled maturity date.

•	During 2010, through a cash tender offer and open market transactions, we repurchased certain of our outstanding series of unsecured notes scheduled to mature in 2011 and 2013. In total, we paid $292.2 million for unsecured notes that had a face value of $279.9 million.

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Throughout the year ended December 31, 2012, we repaid five secured loans totaling $102.1 million, which had a weighted average stated interest rate of 6.08%, at their maturity dates. This compares to payoffs of $12.8 million in 2011, comprised of four individually insignificant secured loans, and $195.4 million in 2010, which was secured debt that we assumed upon the July 2010 acquisition of our joint venture partner's 50% interest in Dugan.

•	We increased net borrowings on the Partnership's $850.0 million line of credit by $285.0 million for the year ended December 31, 2012, compared to a decrease of $175.0 million in 2011 and an increase of $175.0 million in 2010.

•	We paid cash dividends or distributions of $0.68 per common share or per Common Unit in each of the years ended December 31, 2012, 2011 and 2010.

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(1)	Our long-term debt consists of both secured and unsecured debt and includes both principal and interest. Interest expense for variable rate debt was calculated using the interest rates as of December 31, 2012.

(2)	Our unsecured line of credit consists of an operating line of credit that matures December 2015. Interest expense for our unsecured line of credit was calculated using the most recent stated interest rate that was in effect.

(3)	Our share of unconsolidated joint venture debt includes both principal and interest. Interest expense for variable rate debt was calculated using the interest rate at December 31, 2012.

(4)	Represents estimated remaining costs on the completion of owned development projects and third-party construction projects.

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(a)	The following documents are filed as part of this Annual Report:

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(b)	Exhibits

(c)	Financial Statement Schedule

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•	Pertain to the maintenance of records that in reasonable detail accurately and fairly reflect the transactions and dispositions of assets of the company;

•	Provide reasonable assurance that transactions are recorded as necessary to permit preparation of financial statements in accordance with generally accepted accounting principles, and that receipts and expenditures of the company are being made only in accordance with authorizations of management and directors of the company; and

•	Provide reasonable assurance regarding prevention or timely detection of unauthorized acquisition, use or disposition of the company's assets that could have a material effect on the financial statements.

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•	Pertain to the maintenance of records that in reasonable detail accurately and fairly reflect the transactions and dispositions of assets of the Partnership;

•	Provide reasonable assurance that transactions are recorded as necessary to permit preparation of financial statements in accordance with generally accepted accounting principles, and that receipts and expenditures of the company are being made only in accordance with authorizations of management and directors of the General Partner; and

•	Provide reasonable assurance regarding prevention or timely detection of unauthorized acquisition, use or disposition of the Partnership's assets that could have a material effect on the financial statements.

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(1)	The Company

(2)	The Summary of Significant Accounting Policies

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(1)

We are party to guarantees of the third-party debt of these joint ventures and our maximum loss exposure is equal to the maximum monetary obligation pursuant to the guarantee agreements. We have also recorded a liability for our probable future obligation under a guarantee to the lender of one of these ventures, which is included within the carrying value of our guarantee obligations. Pursuant to an agreement with the lender, we may make partner loans to this joint venture that will reduce our maximum guarantee obligation on a dollar-for-dollar basis. The carrying value of our recorded guarantee obligations is included in other liabilities in our Consolidated Balance Sheets.

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(3)	Significant Acquisitions and Dispositions

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(4)	Related Party Transactions

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(5)	Investments in Unconsolidated Companies

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(6)	Discontinued Operations and Assets Held for Sale

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(7)	Indebtedness

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•	In October 2012, we repaid $50.0 million of medium term notes, which had an effective interest rate of 5.45%, at their scheduled maturity date.

•	In September 2012, we issued $300.0 million of unsecured notes that bear interest at 3.875%, have an effective rate of 3.925%, and mature on October 15, 2022.

•	In August 2012, we repaid $150.0 million of senior unsecured notes, which had an effective interest rate of 6.01%, at their scheduled maturity date.

•	In July 2012, one of our consolidated subsidiaries repaid $21.0 million of variable rate unsecured debt, which bore interest at a rate of LIBOR plus 0.85%, at its scheduled maturity date.

•	In June 2012, we issued $300.0 million of senior unsecured notes that bear interest at 4.375%, have an effective rate of 4.466% and mature on June 15, 2022.

•	In December 2011, we repaid $167.6 million of our 3.75% Exchangeable Notes at their scheduled maturity date. Due to accounting requirements, which required us to record interest expense on this debt at a similar rate as could have been obtained for non-convertible debt, this debt had an effective interest rate of 5.62%.

•	In August 2011, we repaid $122.5 million of senior unsecured notes, which had an effective interest rate of 5.69%, at their scheduled maturity date.

•	In March 2011, we repaid $42.5 million of senior unsecured notes, which had an effective interest rate of 6.96%, at their scheduled maturity date.

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(8)	Segment Reporting

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(9)	Leasing Activity

(10)	Employee Benefit Plans

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(11)	Shareholders' Equity of the General Partner and Partners' Capital of the Partnership

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(12)	Stock Based Compensation

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(13)	Financial Instruments

(14)	Commitments and Contingencies

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(15)	Subsequent Events

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(1)	The tax basis (in thousands) of our real estate assets at December 31, 2012 was approximately $7,056,492 for federal income tax purposes.

(2)	Depreciation of real estate is computed using the straight-line method over 40 years for buildings and 15 years for land improvements for properties that we develop, 30 years for buildings and 10 years for land improvements for properties that we acquire, and shorter periods based on lease terms (generally 3 to 10 years) for tenant improvements.

(3)	We hold legal title to these buildings but, for accounting purposes, are treated as direct financing leases. Due to being immaterial for separate presentation, we have classified these buildings within real estate investments and have included them in this schedule.

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