In part 2 (view all entries) of our review of the Atlas of Global Christianity, we will be discussing methodology. Methodology, to a project of the size and scope of the Atlas of Global Christianity is a critical concern. How can all those numbers be verified? The origins of this project are not limited to the research and publication of the Atlas itself. While the Atlas is a self-contained project, it nevertheless builds off 25 years of prior international religious demography research, and the research methods developed for studying Christian denominations by editor emeritus Richard A. Barrett, which resulted in his 1982 publication of the World Christian Encyclopedia.
The Atlas uses the methods developed by prior researches, especially those developed by Barrett. Additionally, the atlas analyzed new sources of material including government censuses, denominational records, and monographs and studies published by scholars, including the World Christian Encyclopedia (1982), the World Christian Database (updated through 2005 and reviewed by Atlas researches through 2008), and the World Religion Database (2008).
The major methodological assumption here is that by gathering 
statistics from various reporting agencies over the long term, and meshing them against the continual emergence of new statistics, a coherent (not perfect) picture of what Christianity looks like demographically on the world map, can be generated. The strength of this perspective lies in its understanding that Christianity is religious movement, not a static entity. While the data and statistics change–even on a day-to-day basis, the goal of the Atlas is not to provide exact understanding but to provide a documentation of how the story of Christianity is unfolding at the global, continental, and provincial levels.
The weakness of this approach is that does not and cannot determine the qualia, orthodoxy, or cultural expression of Christianity on any level. It cannot scratch below the surface of the numbers. But why should it do that? This is a weakness any scientific study of a 
human phenomena would face. It si impossible for a religion as large and culturally diverse as Christianity to be measured in this fashion; it is not a monolith.
In my judgment the Atlas of Global Christianity has accomplished this task, the task of documenting the current state of Christianity, and its relationship to other religions in extraordinary fashion. Its methodological strengths, the accumulation of data over a long-period, the recognition of the relativity and subjectivity of sources data coupled with the implementation of tools and strategies to hedge those influences allows the Atlas to present a highly credible articulation and documentation of Christianity’s presence on the globe.
