Urbanites earn three times as much as rural dwellers on average, according to the report. In 2005 the top 10 percent of city earners earned nine times as much as the poorest 10 percent and in rural areas the gap was a factor of 7.

    Income disparity is sector and rank-sensitive, the report notes.

    Between 1990 and 2005, salaries rose faster in state-owned enterprises and institutions than in other organizations.

    People employed in banks, insurance companies, post, telecoms and power businesses did better overall than workers in the mining, construction, forestry, animal husbandry and fishery sectors. Managers did better than workers.

    According to Su Hainan, head of the salary department of the China Labor Society, the monopoly status of some state-owned businesses made it easier for them to grant pay rises.

    Su Hainan said that as the migrant worker phenomenon amplifies, salaries and wages are making up a bigger share of rural residents' income, up from 45 percent in 1990 to 63 percent in 2005.

    In cities salaries represent about three quarters of residents' income, with other sources of revenue including rental and investment income and earnings from patents.

    The report said that government efforts to narrow the income gap between rich and poor and between rural and urban areas had so far had little effect.