Solution :
One of the argument that the low income countries will not have an advantage in achieving a high productivity of the workers as the economic growth in the near future is the increasing in marginal returns.
It occurs only when any addition in the variable input (i.e. labor) to a fixed input (i.e. capital) enables such variables input to be more productive. In other words, 2 workers are more than twice as productive as 1 worker and 4 workers are more than twice as productive as 2 workers.