• This is also known as the ratio method of forecasting future population. In this method the census population record is expressed as the percentage of the population of the whole country. The population of the city under consideration and the country's population for the last four to five decades are collected from the census department.

• The ratio of the town under consideration to the national population is calculated for these decades. Now a graph is plotted between these ratios and the time. The extension of this graph will give the ratio corresponding to the future years for which the forecasting of population is to be done.

• The ratio so obtained is multiplied by the expected national population at the end of the designed period, for determing the expected national population of the town under reference.

• This method is suitable for those towns and cities whose development is likely to take place according to the national growth.