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The population registration system still has important functions.

It supplies local data which are useful in administration and which can be used as a basis for intensive studies in particular situations.

It provides a frame for the sampling census.

It also provides a frame within which the registration of vital events is gradually gaining force ( though one cannot expect to obtain reliable vital statistics in most parts of the Congo from this source in the near future ).

It is still used in making current population estimates in post-census years, though the value of these estimates is open to question.

Finally, it may have certain very important, less obvious values.

Even though the registers may have an incomplete record of persons present in a particular area or include persons no longer living there, they contain precise information on ages, by date of birth, for some of the persons present ( especially children in relatively stable communities ) and supplementary information ( such as records of marital status ) for many others.

The quality of the census data can, therefore, be greatly improved by the use of the registration records in conjunction with the field inquiries.

Furthermore, it may be possible to estimate the error due to bias in method ( as distinguished from sampling error ) in each of these sources, on such subjects as fertility, mortality, and migration during a given interval by using information from two largely independent sources in conjunction.