The six [five] Manuals in this cluster explain methods for estimating population size, mortality and fertility with the emphasis on situations when data from censuses and civil registration are insufficient or unreliable. In addition, Manual II is devoted entirely to the methods of appraising the quality of basis data for demographic estimates. The objective of any analysis determines the appropriate indicators which vary from basic to quite sophisticated. More complex indicators typically require deeper knowledge of demography. This is why the Manuals differ in format and presentation style from step-by-step guides to comprehensive explanations of the techniques. Manual X is the backbone of this cluster for it is a particularly large and coherent compilation of techniques suited for the analysis of incomplete or defective demographic data. Since the demographic estimates constitute the basis of any field of demographic analysis, all other Manuals on this website are related to this cluster. Particularly strong ties connect this cluster to the clusters Demographic models and Population projections.