THAT rich countries have already produced more than their fair share of global carbon-dioxide emissions is one fact complicating negotiations for a new global climate-change treaty. In its annual “World Development Report” published on Tuesday September 15th, the World Bank notes that they accounted for 64% of global CO2 emissions from fossil fuels between 1850 and 2005. In 2005 itself, however, this share had fallen to 50%, and middle-income countries such as India and China (now the world’s biggest emitter) accounted for almost half of CO2 emissions and more than half of wider greenhouse-gas emissions. But rich countries’ 1 billion people emit far more on a per person basis compared with the 4.2 billion people who live in middle-income countries. The report notes that by reducing their own heavy carbon footprints and investing in new technology, rich countries would be more effective in persuading poorer countries to do likewise.