In the past, developmental psychologists have not always done a significant amount of research on development beyond adolescence. today, they study the whole of the human life span. why do you suppose this change has occurred? in other words, why do they place a greater emphasis on studying how we change later in life, beyond childhood and adolescence?

Increased life expectancy lies at the heart of the matter

Explanation:

In the past, developmental psychologists have not always done a significant amount of research on development beyond adolescence. Today, they study the whole of the human life span.I suppose this change has occurred because as life expectancy increases adults continue to mature and develop in physical, cognitive, and social ways. Phycholgists place a place a greater emphasis on studying how we change later in life because more data from research will be necessary as the elderly population continues to grow.  

citizens were able to charge more for their goods and services