The catch-up effect refers to the fact that a

The catch-up effect refers to the fact that b. it is easier for a country to grow fast if it starts out relatively poor .

Since relatively poor countries grow at a much faster rate than the rich countries. Therefore, all countries tend to converge at the same level of per capita income. It is because as compared with the rich countries, poor countries have more availability of opportunities for growth as they are given prepared and experimented technologies and application of technology by the rich countries. They generally copy the production methods from other developed countries which would cost them the least cost of research and development. Hence, they act as free-rider on the discoveries of other nations. As a result, they get successful as to converge with the per capita income of other countries.