Absolute convergence is the idea that the output per capita of developing countries will match developed countries, regardless of their specific characteristics. This argument builds on the fact that developing countries have a lower ratio of capital per worker compared to developed countries.
With lower capital, developing countries will enjoy higher marginal productivity of capital than developed countries. As a result, developing countries runs a higher economic growth than developed countries, leading to the income in both will eventually converge.
However, the idea has not been proven right, at least until now. Developing countries are still difficult to catch up with developed countries. Why that?
As in the Solow growth model, other factors influence output, namely technological knowledge or total factor productivity. These factors are the engine of growth in developed countries, making it difficult for developing countries to match them.