Migration Statistics, Population Accounts and Life Tables – the Methodology Used in Bulgaria

Vital statistics in Bulgaria are considered to be comparatively detailed, complete and precise. Professionals at the National Statistical Institute prefer to use these data together with more direct methods to produce life tables with single year age groups separately for males and females. However, external migration might present a conceptual problem for such methods, while more sophisticated methodologies might not be applicable because migration data are usually scarce and very unreliable. Migration might affect the derivation of life tables in two main ways. First, migration is a competitive risk to mortality and should be encompassed carefully, particularly for years with a high number of emigrants as is the typical case for Bulgaria. Secondly, loose migration registration or any other deficiencies or distortions in migration data might appear to pose a serous problem in the use of population accounts in life table calculations, and for statistical analysis in general. Toward the end of the 1960s there was a significant outflow of migrants to Turkey which was never mirrored by statistical data in the same detail as mortality. Underground and illicit emigration from Bulgaria after World War II and the massive departure of Turks during the 1980s might also have been a factor in misjudging the size of population groups between censuses and, hence, under- or overestimating mortality. Given the reluctance of the political authorities at that time to reveal these facts to the public, it was very difficult for statisticians to obtain relevant data, perform life table calculations in a consistent manner or produce reliable demographic analysis. This paper examines the methodology of the Institute and addresses some related issues made upon observations of the practice of the official statistics in Bulgaria in this area