Explanation:

The idea of convergence in economics (also sometimes known as the catch-up effect) is the hypothesis that poorer economies' per capita incomes will tend to grow at faster rates than richer economies. As a result, all economies should eventually converge in terms of per capita income.
From the survey 2017-18:
Convergence happens essentially through trade and through mobility of factors of production. If a state/country is poor, the returns to capital must be high and should be able to attract capital and labor, thereby raising its productivity and enabling catch up with richer states/countries. Trade, based on comparative advantage, is really a surrogate for the movement of underlying factors of production as Samuelson pointed out early on. A less developed country that has abundant labor and scarce capital will export labor-intensive goods (a surrogate for exporting unskilled labor) and imports capital-intensive goods (a surrogate for attracting capital).