Beware the Passenger Card! Australian and New Zealand Data on Population Movement between the Two Countries 1

Abstract

Studies of international migration frequently make use of data collected as part of the administrative procedure through which persons entering or leaving a country by an approved route pass. Such databases often are used quite uncritically. This article reports on idiosyncrasies of two official national migration databases, most of which became apparent when trying to account for marked differences in their estimates of both migratory and more short-term population movement between the two countries, and for variation over time in the pattern of differences. It is shown that the use of apparently similar broad classification principles, by different countries and through time within a country, can create impressions of comparability and continuity that may be quite misleading. Before using data of this type one should examine carefully how subsidiary classification concepts have been defined and the manner in which both these and the broader principles have been translated into questions on travel documents and data processing conventions.