Harriet S.MeyerMD, Contributing EditorDavid H.MorseMS, Journal Review EditorRobertHoganMD, adviser for new media
Beyond Six Billion deals with one of the most important issues in the field of demography: population forecasts. As the authors state in the introduction, this is an area in which demographers are most needed. It is also an area in which issues at the core of the field of demography are mobilized (estimation of population parameters and understanding of the factors affecting these parameters).
The main purpose of the book is to evaluate the methodology and assumptions of current population projections and to give recommendations for their improvement. In this regard, the conclusions are rather blunt. Indeed, the authors conclude that "current world projections to 2050 are based on reasonable assumptions and provide plausible forecasts of world demographic trends for the next few decades." This conclusion is reached after thorough evaluation of the accuracy of past projections and detailed examination of the factors affecting fertility, mortality, and migration, which are the three components of population growth. The leitmotiv is that, when it comes to forecasting fertility, mortality, and migration trends, assumptions are usually crude and simplistic but are difficult to improve on because more complex models do not seem to perform better. The difficulty of predicting demographic trends is particularly obvious in the case of "demographic quakes," ie, large and sudden changes in population growth rates as a result of political, economic, or environmental crises. Thus, the authors are often left with recommendations that are self-evident, for example, their call for updating projections often to take demographic crisis into account. Such an unimposing recommendation is not the result of incomplete investigation of the options available for doing projections. On the contrary, it is an honest acknowledgment of a scientific problem on which it is hard to make progress because of some intrinsic features.
PopulationBeyond Six Billion: Forecasting the World's Population. JAMA. 2002;287(6):781-782. doi:10.1001/jama.287.6.781-JBK0213-3-1