In a move aimed at encouraging the states to improve their performance, the government is planning to modify the Gadgil-Mukherjee formula used for calculating Central assistance given to the states by increasing the performance weightage by 10 per cent. To provide for the 10 per cent increase, there are plans of reducing the weightage for population by 5 per cent. The remaining 5 per cent would be adjusted among the weightages for special problems and per capita income.