Hi, please list out the formulas where necessary , graphs where necessary , if the question doesnt require it, its fine not have it but please do put it down if it helps you to explain .explain it and list out the formulas used with explanations of formulas,themeaning of the symbols. Please dont provide a poor answerThank you!

"Why the Developing World Started Gaining on the West3" by Noah Smith. Noah tells a story about convergence which divides the past 150 years into three eras - what are they and how are they different? What explanation is given for the different patterns of convergence in the "middle" era compared to the latest era?