BEIJING - A think tank has estimated that the county-level economy now accounts for more than half of China's gross domestic product (GDP).

From 2008 on, the GDP of Chinese counties has been growing more rapidly than the nation's average, according to a new report by the Institute of Industrial Economics of the Chinese Academy of Social Sciences.

In 2010, county-level GDP constituted about 49.8 percent of the country's whole economy and the momentum of growth has been retained in recent years, said the report, released earlier this month.

Despite the rapid growth, many problems remain. County-level sectors are small in scale and are growing at great cost in terms of discharges and use of resources, weighing heavily on the environment, said Jin Bei, head of the institute.

To further tap growth potential, counties must upgrade their industries, Jin said.

The report said there are many dissonances between industrialization, urbanization and agricultural modernization, urging better coordination.

China's 2012 GDP grew 7.8 percent year on year, its slowest pace in 13 years.