Coverage and reliability of Chinese statistics regarding sulfur dioxide emissions during the late 1990s

According to official Chinese statistics, sulfur dioxide emissions dropped significantly in the late 1990s before rising again. Some researchers have expressed concern over data reliability, however, and the sample of enterprises represented by sulfur dioxide emission statistics generates only one third of China's industrial output, which may result in undercounting of emissions. In addition, coal production and consumption during the late 1990s may have been undercounted due to politically motivated manipulation of numbers, and this phenomenon may also partly explain the reported reductions in sulfur dioxide emissions. Coal sulfur content derived from coal supply-side information is generally found to be higher than from demand-side information used to calculate emissions for official statistics. Meanwhile, no solid data are available that demonstrate improvement of the desulfurization of smokestack emissions. All of these are potential factors in the underestimation of China's emissions.