Geographia Polonica (1988) vol. 54
Application of two types of migration data to multiregional demographic projections
Geographia Polonica (1988) vol. 54, pp. 43-62
The last two decades have brought an intensive development of various demo-graphic models and thereby an increased interest in the data concerning all the demographic phenomena. Simultaneously, one could observe a tendency towards comparative studies on the results obtained in different countries, with different models and on the basis of diverse data. It is on these grounds that there grew a broad research program, carried out within the International Institute for Applied System Analysis (IIASA) under the leadership of A. Rogers and in collaboration with several dozens of scientists from almost twenty countries. The key to the successful implementation of the program was the adoption of the unified methodology, described in Rogers (1975), i.e. the so-called Rogers model, as well as the application of the widely available program packages (Willekens and Rogers 1978). In spite of unified methodology "... comparabi-lity is, however, severly handicapped by the considerable degree of incomparability of the input data, in particular the migration data." (Rees and Willekens 1981, p.73). This incomparability resulted from different ways of data collection (registration data versus census data) and from differences in the periods for which data were collected.The work presented is an effort at performing a comparative analysis of the results obtained by the Rogers model when two types of migratory data are fed into this model. The analysis was conducted for the three following aspects: (1) mobility patterns of population represented by raw data were compared, (2) results of the Rogers model for two data types were compared, (3) the usefulness of the data on these two types for forecasting purposes was assessed. The hypothesis was adopted, according to which the two data types, used to generate — in the projections — spatial distribution and population structure settings, display specific features.It should be emphasized that the main goal of the work presented is the study of the influence exerted by methods of measuring migration, and not of the migratory behaviour patterns. In view of the methodological nature of this work it was decided to limit the number of regions considered, so as to simplify the making of comparisons. Basing on such assumptions the study concentrated on two regions: urban and rural. Projections were produced separately for women and for the whole of the population, with disaggregation into 18 five — year age groups.