The development of China's four top county-level cities shares many key features, including economic strength, characteristic industries and location, according to experts and officials.

The four are Cixi and Yiwu in Zhejiang province, Kunshan in Jiangsu province, and Jinjiang in Fujian province.

"The location advantage is an important reason for the rapid economic and population development of these four cities," said Ren Yuan, a professor at the Population Research Institute of Fudan University.

"The development of industry and commerce in these cities has benefited from a convenient transportation system with surrounding areas, thus taking advantage of the development of metropolitan circles, central cities in urban agglomerations and neighboring cities," Ren said.

They are all located in the nation's eastern coastal areas, which provide cities with the opportunity to become much larger.