Which factor has been responsible for the declining death rate in many of the world’s less industrialized nations?

The answer is Improved health.  This is the factor that has been responsible for the declining death rate in many of the world’s less industrialized nations.  Death rates have been declining as human longevity has been increasing. Increased sanitation and better disease care are some factors that contributed to a decline in death rate.,

The peak above is part of the  sierra madre occidentals ,  a chain of volcanic mountains that runs through the middle of central america. 

It just all depends on where you live at the moment