around $33 bn annually, i.e., an order of magnitude less than the "carbon tax [which] has by far the greatest revenue-raising potential, estimated at $130-750 bn annually." The author warns however that both these market-based revenue estimates "are necessarily speculative", and he has more confidence in the revenue-raising potential of "The International Finance Facility (IFF) and International Finance Facility for Immunisation (IFFIm)." Is the tax easy to avoid? Technical feasibility Although Tobin had said his own tax idea was unfeasible in practice, Joseph Stiglitz, former Senior Vice President and Chief Economist of the World Bank, said, on October 5, 2009, that modern technology meant that was no longer the case. Stiglitz said, the tax is "much more feasible today" than a few decades ago, when Tobin recanted. However, on November 7, 2009, at the G20 finance ministers summit in Scotland, Dominique Strauss-Khan, head of the International Monetary Fund, said "transactions are very difficult to measure and so it's very easy to avoid a transaction tax." Nevertheless, in early December 2009, economist Stephany Griffith-Jones agreed that the "greater centralisation and automisation of the exchanges and banks clearing and settlements systems ... makes avoidance of payment more difficult and less desirable." In January 2010, feasibility of the tax was supported and clarified by researcher Rodney Schmidt, who noted "it is technically easy to collect a financial tax from exchanges ... transactions taxes can be collected by the central counterparty at the point of the trade, or automatically in the clearing or settlement process." (All large-value financial transactions go through three steps. First dealers agree to a trade; then the dealers' banks match the two sides of the trade through an electronic central clearing system; and finally, the two individual financial instruments are transferred simultaneously to a central settlement system. Thus a tax can be collected at the few places where all trades are ultimately cleared or settled.) Based on digital technology, a new form of taxation, levied on bank transactions, was successfully used in Brazil from 1993 to 2007 and proved to be evasion-proof, more efficient and less costly than orthodox tax models. In his book, Bank transactions: pathway to the single tax ideal, Marcos Cintra carries out a qualitative and quantitative in-depth comparison of the efficiency, equity and compliance costs of a bank transactions tax relative to orthodox tax systems, and opens new perspectives for the use of modern banking technology