James M. Poterba, Nirupama Rao & Jeri Seidman (MIT, Department of Economics) have posted The Significance and Composition of Deferred Tax Assets and Liabilities on SSRN.  Here is the abstract:

This paper investigates the importance of deferred tax assets and liabilities for a sample of large U.S. corporations between 1993 and 2004 and documents substantial heterogeneity in the deferred tax positions of different firms. In 2004, 25 firms in a sample of 73 reported net deferred tax assets and 48 reported net deferred tax liabilities. Firms differ substantially in the composition of their deferred tax assets and liabilities. The largest components of deferred tax assets for sample firms are Loss and Credit Carryforwards and Employment and Post-employment Benefits. The largest components of deferred tax liabilities are Property, Plant & Equipment and Leases. Total deferred tax assets for sample firms with net deferred tax assets in 2004 were $61.9 billion, while total deferred tax liabilities for sample firms with net deferred tax liabilities were $223.8 billion. A five percentage point decline in the federal statutory corporate tax rate could reduce net income at sample firms with net deferred tax assets by as much as $8.8 billion, since a statutory rate cut would reduce the value of deferred tax assets and this change would be reflected on the income statement. We use data on the sales, market value, and assets of sample firms, relative to aggregate data for the U.S. corporate sector, to estimate the aggregate value of deferred tax assets and liabilities.