There’s a “convergence” theory in economics that suggests, over time, that “poor nations should catch up with rich nations.”
But in the real world, that seems to be the exception rather than the rule.
There’s an interesting and informative article at the St. Louis Federal Reserve Bank which explores this theory. It asks why most low-income and middle-income nations are not “converging” with countries from the developed world.
…only a few countries have been able to catch up with the high per capita income levels of the developed world and stay there. By American living standards (as representative of the developed world), most developing countries since 1960 have remained or been “trapped” at a constant low-income level relative to the U.S. This “low- or middle-income trap” phenomenon raises concern about the validity of the neoclassical growth theory, which predicts global economic convergence. Specifically, the Solow growth model suggests that income levels in poor economies will grow relatively faster than developed nations and eventually converge or catch up to these economies through capital accumulation… But, with just a few exceptions, that is not happening.
Here’s a chart showing examples of nations that are – and aren’t – converging with the United States.