Although per capita emissions of S02 and NOx are lower, emissions relative to GDP, an indicator of environmental efficiency, are high compared with large and medium-sized OECD countries (Figure 2.1, Panel C). Pollution intensity refers to 2010 or most recent observation. Though the incidence of acid rain in China has declined somewhat in recent years, it remains a serious concern. In 2011 the government estimated that over 10% of China’s landmass was affected, including farmlands and densely populated areas along the Yangtze River and in the South-East (MEP, 2012).