Read this: Over the course of the 20th century, the world's per-capita gross domestic product grew by a factor of five, much more than all earlier centuries combined (including the 19th with its Industrial Revolution). Many economists make the case that this understates the magnitude of growth, as many of the goods and services consumed at the end of the 20th century, such as improved medicine (causing world life expectancy to increase by more than two decades) and communications technologies, were not available at any price at its beginning. However, the gulf between the world's rich and poor grew wider, and the majority of the global population remained in the poor side of the divide.

What has Modern medicine increased the average life expectancy by?
What is the answer? (If it cannot be answered, return "unanswerable")
two decades