I want to know the answer to the following question:
By what percentage did the world's per-capita gross domestic product grow by during the 20th century?
All the background I'm provided with is that "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.". Is that enough to answer the question?
Answer: no