What can we learn about uncertain tax benefits from FIN 48?

FIN 48, Accounting for Uncertainty in Income Taxes, standardizes accounting for uncertain tax benefits and requires companies to disclose their tax reserve amounts. We summarize hand-collected disclosures related to tax reserves from 2005 through the first quarter of 2007. For the largest 100 non financial, non-regulated firms, the reserve at adoption on January 1, 2007 is $78 billion excluding interest, or about two percent of assets. Of this $78 billion, an estimated $58 billion would affect earnings if ever released.