Exhibit 12

ERP OPERATING LIMITED PARTNERSHIP
Consolidated Historical
Computation of Ratio of Earnings to Combined Fixed Charges

|                                                                                                                                                                                                                                                       |                                                                                    | Historical
|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ | ---------------------------------------------------------------------------------- | ----------
|
|
|Income before allocation to Minority Interests, income from investments in unconsolidated entities, net gain on sales of unconsolidated entities, discontinued operations, extraordinary items and cumulative effect of change
in accounting principle |                                                                                    | $         
|                                                                                                                                                                                                                                                       | Interest and other financing costs                                                 |           
|                                                                                                                                                                                                                                                       | Amortization of deferred financing costs                                           |           
|                                                                                                                                                                                                                                                       | Income from investments in unconsolidated entities                                 |           
|                                                                                                                                                                                                                                                       |                                                                                    |           
|Earnings before combined fixed charges and preferred distributions                                                                                                                                                                                     |                                                                                    |           
|                                                                                                                                                                                                                                                       | Preferred distributions                                                            |           
|                                                                                                                                                                                                                                                       |                                                                                    |           
|Earnings before combined fixed charges                                                                                                                                                                                                                 |                                                                                    | $         
|                                                                                                                                                                                                                                                       |                                                                                    |           
|                                                                                                                                                                                                                                                       | Interest and other financing costs                                                 |           
|                                                                                                                                                                                                                                                       | Amortization of deferred financing costs                                           |           
|                                                                                                                                                                                                                                                       | Interest capitalized for real estate and unconsolidated entities under development |           
|                                                                                                                                                                                                                                                       |                                                                                    |           
|Total combined fixed charges                                                                                                                                                                                                                           |                                                                                    |           
|                                                                                                                                                                                                                                                       | Preferred distributions                                                            |           
|                                                                                                                                                                                                                                                       |                                                                                    |           
|Total combined fixed charges and preferred distributions                                                                                                                                                                                               |                                                                                    | $         
|                                                                                                                                                                                                                                                       |                                                                                    |           
|Ratio of earnings before combined fixed charges to total combined fixed charges                                                                                                                                                                        |                                                                                    |           
|                                                                                                                                                                                                                                                       |                                                                                    |           
|Ratio of earnings before combined fixed charges and preferred distributions to total combined fixed charges and preferred distributions                                                                                                                |                                                                                    |           
|                                                                                                                                                                                                                                                       |                                                                                    |           

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