These studies are often neglected in Epidemiology textbooks because they are not viewed as "scientific" enough. What is often forgotten is the work of early epidemiologists consisted of the faithful gathering of vital statistics by such men as John Graunt and William Farr.
However, epidemiologists know the value of such data and systematically collect data through surveillance activities.
National bastions of Public Health like the Centers for Disease Control & Prevention (CDC) are well known for gathering such statistics.
Surveillance data allow public health practitioners to look at patterns and trends in disease distribution, as well as provide the basis with which to monitor and evaluate the effectiveness of public health interventions in controlling the spread of disease.