12 May 2008 — Cologne, Germany and Washington, DC - May 7, 2008. The value of trading in the carbon market more than doubled in 2007 to $64 billion, according to the World Bank`s annual report, "State and Trends of the Carbon Market." The $64 billion was comprised of approximately $50 billion in allowance transactions and more than $13.5 billion in transactions of project-based emission reductions. Traded volumes also increased.