Year-end level from BEA, Fixed Asset Table 4.1 Current-Cost Net Stock of Private Nonresidential Fixed Assets by Industry Group and Legal Form of Organization; line 39, corporate nonfinancial, Structures. Other quarter's levels are derived from year-end level, plus the quarterly unadjusted flow calculated as gross investment (FOF series FU105013063) less depreciation (FOF series FU106330063), plus other volume changes and capital gains. Other volume changes are from unpublished BEA data on nonfinancial corporate business disaster losses on nonresidential structures (a portion of NIPA, Table 5.1. Saving and Investment, line 60, Disaster losses, Domestic business), with the opposite sign. Capital gains are estimated based on NIPA, table 1.1.4 Price Indexes for Gross Domestic Product, line 10, Nonresidential, Structures.