Current and future worldwide prevalence of dependency, its relationship to total population, and dependency ratios.

Bulletin of the World Health Organization, April, 2004 by Rowan H. Harwood

Introduction

There were major changes in population structures and disease patterns in the last century in economically more developed countries (the so-called demographic and epidemiological transitions). Other countries are currently experiencing these transitions, or will do so in the coming decades.

The "demographic transition" describes the shift from high fertility and high mortality, to low fertility and low mortality. This results in increasing life expectancy and an increasing proportion of elderly people in the population. The "epidemiological transition" describes the change from a predominance of infectious diseases, with high maternal and child mortality, to a predominance of chronic diseases.

An important effect of chronic diseases is...