Sanitary Action

Human beings evolved under conditions of high mortality due to famines, accidents, illnesses, infections and
war and therefore the relatively high fertility rates were essential for species survival. In spite of the relatively
high fertility rates it took all the time from evolution of mankind to the middle of the 19 century for the global
population to reach one billion. The twentieth century witnessed an unprecedented rapid improvement in
health care technologies and access to health care all over the world; as a result there was a steep fall in the
mortality and steep increase in longevity. The population realized these changes and took steps to reduce
their fertility but the decline in fertility was not so steep. As a result the global population has undergone a
fourfold increase in a hundred years and has reached 6 billion.
Demographers refer to these changes from stable population with high fertility and mortality to a new stability
in population due to low fertility and mortality patterns as demographic transition. Demographic transition
occurs in four phases; of these the first three phases are characterized by population growth. In the first
phase there is a fall in death rate and improvement in longevity; this leads to population growth. In the
second phase there is a fall in birth rate but fall is less steep than fall in death rates and consequently there
is population growth. In the third phase death rates plateau and replacement level of fertility is attained but
the population growth continues because of the large size of population in reproductive age group. The
fourth phase is characterized by fall in birth rate to below replacement level and reduction in the proportion of
the population in reproductive age group; as a result of these changes population growth ceases and
population stabilizes. Experience in some of the...