Rental properties and properties under development are individually evaluated for impairment when conditions exist which may indicate that it is probable that the sum of expected future undiscounted  cash flows is less than the carrying amount of the property. Upon determination that impairment  has occurred, a write-down is recorded to reduce the carrying amount of the property to its estimated fair value.  improvements, 40 years for buildings and building improvements, the respective lease term for tenant improvements and the estimated useful life for equipment.The values of above and below market leas- es are amortized over the life of the related lease and recorded as either an increase (for below market leases) or a decrease (for above market leases) to rental income.The values of at-market leases and orig- ination costs are classified as leasing costs, included in other assets on our balance sheets and amortized over the remaining life of the lease.  In accordance with Statement of Financial Accounting Standards No. 34, “Capitalization of Interest Cost” (“SFAS 34”) and Statement of Financial Accounting Standards No. 67,“Accounting for Costs and Initial Rental Operations of Real Estate Projects” (“SFAS 67”), we capitalize direct construction and development costs, including predevelopment costs, interest, property taxes, insurance and other costs directly related and essential to the acquisition, development or construction of a project. Pursuant to SFAS 34 and SFAS 67, capitalization of construction and development costs is required while activities are ongoing to prepare an asset for its intended use. Costs incurred after a project is substantially com- plete and ready for its intended use are expensed as incurred. Costs previously capitalized related to abandoned acquisition or development opportunities are written-off. Should development activity cease, a portion of interest, property taxes, insurance and certain costs would no longer be eligible for capitalization, and would be expensed as incurred. Expenditures for repairs and maintenance are expensed as incurred. We also capitalize costs directly related and essential to our leasing activities.These costs are amortized on a straight-line basis over the terms of the related leases. Costs that were previously capitalized and which related to unsuccessful leasing opportunities are written-off.  We hold equity investments in certain publicly-traded companies and privately held entities primarily involved in the life science industry.All of our investments in publicly-traded companies are considered “available for sale” in accordance with Statement of Financial Accounting Standards No. 115, “Accounting for Certain Investments in Debt and Equity Securities” (“SFAS 115”), and are recorded at fair value. Fair value has been determined as the closing trading price at the balance sheet date, with unrealized gains and losses shown as a separate component of stockholders’ equity.The classification of investments under SFAS 115 is determined at the time each investment is made, and such determina- tion is reevaluated at each balance sheet date.The cost of investments sold is determined by the specif- ic identification method, with net realized gains included in other income. Investments in privately held entities are generally accounted for under the cost method because we do not influence any operating or financial policies of the entities in which we invest. Certain invest- ments are accounted for under the equity method in accordance with Accounting Principles Board Opinion No. 18, “The Equity Method of Accounting for Investments in Common Stock” and Emerging Issues Task Force Topic D-46,“Accounting for Limited Partnership Investments”. Under the equity method of accounting, we record our investment initially at cost and adjust the carrying amount of the investment to recognize our share of the earnings or losses of the investee subsequent to the date of our investment.  For all of our investments, if a decline in the fair value of an investment below its carrying value is determined to be other than temporary, such investment is written-down to its estimated fair value with a non-cash charge to current earnings.The factors that we consider in making these assessments include, but are not limited to, market prices, market conditions, financial condition, prospects for favorable or unfavorable clinical trial results, new product initiatives and/or sales, and new collaborative agreements. P 6 Accounting for Investments  Capitalization of Costs