BEIJING -- The ratio of income earned by urbanites to that of rural residents is about 5.2, said a blue paper released by a major government think tank on Tuesday.

According to The Urban Blue Book: China City Development Report No 5, published by the Chinese Academy of Social Sciences, the ratio of urbanites' disposable income to rural residents' net income reached 3.13 last year.

As about 40 percent of farmers' net income was used to purchase chemical fertilizer, pesticide, seeds and other means of production, deducting these expenses, China's urban income was about 5.2 times that of the countryside, said the report.

The figure for income gap is about 26 percent higher than that of 1997 and 68 percent higher than that of 1985, it said, adding it far exceeded figures of the same kind in many foreign countries.

The Urban Blue Book also noted that the number of urbanites has surpassed the number of rural residents in China, with the urbanization rate reaching 51.27 percent, a significant change in the country's social structure which ushers in an era of "city-based society."

However, there is still a long way to go for China to become truly city-based, it argued, as the majority of migrant workers and farmers-turned-city dwellers find it hard to blend into urban life, and most Chinese cities lack distinguished features and cultures.

The next five to 10 years are a key period for China to turn from a village-based to a city-based country and enhance the quality of urbanization, the report said.