Adjusting Census Figures

Why adjusting census figures ? Errors may be substantial and the validity of the counts delivered by the census is in question Coverage of certain population groups may be deficient, some parts of the country may be disadvantaged in terms of financial repartition (attribution of funds, of seats…) But if the undercoverage is uniform, there is no consequences in terms of equity To have a correct estimate of the population as a basis for future intercensal estimates and projections NSO may consider to adjust the census counts using information from the evaluation studies 2

Adjusting Census Figures What to adjust ? Census results Total population, population by administrative area (state, region, …) Main distributions (by state, sex, age…) All the database, in order to adjust all potential distribution 3

How to adjust ? Depending on the range of the evaluation programme associated with the census, NSO may carry out more than one type of study to evaluate the census Combining the estimates has the advantage of taking the best characteristics to counterbalance weaknesses in the evaluation methods For example, estimates from demographic analysis may only provide national totals, but those may be considered better estimates than those estimated from PES PES may provide more geographical detail than demographic methods 4

How to adjust ? There are several techniques to adjust census figures Coverage rate can be directly used to adjust population size The methods of synthetic estimation and regression permit modeling the distribution of the undercount at the level of geography appropriate to the measurement technique The modeling process for synthetic estimation is to estimate the mean undercount rate (persons missed as a percent of total estimated population) for various demographic subgroups at a certain geographic level. This method takes undercount at high levels of geography and distributes it proportionally at lower levels of geography 5 5

How to adjust ? Regression techniques fits a regression model to the undercount estimates for a set of geographic areas. The estimates are generated similar to that used for synthetic estimation by applying the coefficients estimated at a larger geographic areas to characteristics and variables observed in lower geographical levels Synthetic estimates are guaranteed to sum to estimates of undercount generated at higher levels, while estimates from regression techniques are not guaranteed to sum to the demographic estimated formed for each region

Population estimates/projections Census results can be adjusted for purposes of population estimates and projections Based on the result of census evaluation, population size can be adjusted to take into account undercoverage or over coverage Distribution of population by age can be adjusted to take into account age misreporting Demographic estimates such as the level of fertility and mortality can be adjusted for coverage and distribution errors

Adjusting Census Figures Some considerations Consequences of making adjustment might be critical and sensitive Adjustments have an effect on geographic and demographic distributions of population Adjustment may be costly (in doing and in explaining) Adjustment requires specific communication Adjustment may be complex and time consuming 8

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