An expert panel led by Kofi Annan, a former UN secretary-general, looked at five deals struck between 2010 and 2012, and compared the sums for which government-owned mines were sold with independent assessments of their value. It found a gap of $1.36 billion, double the state’s annual budget for health and education. And these deals are just a small subset of all the bargains struck, says the report, which Mr Annan presented in Cape Town, South Africa, on May 10th.

The report highlights some puzzling details. For instance ENRC, a London-listed Kazakh mining firm, waived its rights to buy out a stake in a mining enterprise owned by Gécamines, Congo’s state miner, only to acquire it for $75m from a company owned by Dan Gertler, an Israeli businessman, which had paid $15m for it just months earlier. Mr Gertler is close to Joseph Kabila, Congo’s president. ENRC, which is being investigated by the Serious Fraud Office in Britain, was Congo’s third-largest copper producer last year. Both ENRC and Mr Gertler deny wrongdoing.

African countries often fail to collect reasonable taxes on mining, says Mr Annan’s panel. For example, Zambia’s copper exports were worth $10 billion in 2011, but its tax receipts from mining were a meagre $240m. The widespread use by mining firms of offshore investment vehicles as conduits for profits creates scope for tax avoidance. Their use is not restricted to rich-world companies. Much of the oil that Angola ships to China is via a company called the China International Fund. Its trading prices are not made public…

Congo’s prime minister, Matata Ponyo Mapon, promises change. In January 2013… Mr Ponyo said he would rein in the state-owned mining companies and increase transparency in the industry. “We must avoid situations where we’re not publishing our mining contracts, where our state assets are undervalued, and where the government doesn’t know what its state mining companies are doing,” he told miners and officials at a conference in January….

Last year miners in Congo, which include Freeport-McMoRan and Glencore Xstrata, shipped $6.7 billion-worth of copper and cobalt from the country.

Business in the Democratic Republic of Congo: Murky minerals, Economist, May 18, 2013, at 74