The 20th century was broadly characterized by divergence between high-income countries and the developing world, with only a limited number (less than 10 percent of the economies in the world) managing to progress out of lower or middle-income status to high-income status. The last decade witnessed a sharp reversal from a pattern of divergence to convergence—particularly for a set of large middle-income countries. The latter phenomenon was also driven by increasing economic ties among developing countries, and on the intellectual scale, increased knowledge generation and sharing among the developing countries. Re-thinking development policy implies confronting these realities: 20th century economic divergence, the experience of the handful of success stories, and the recent rise of the multi-polar growth world. The paper provides descriptive data and a literature survey to document these trends.
That is from the abstract of the new paper "Shifting Patterns of Economic Growth and Rethinking Development" by Lin and Rosenblatt (April 2012).
In the paper there are several interesting graphs and a chronological map of theories and thinkers in economic development since Adam Smith.
This graph of China is interesting although it does not refer directly to the issue of cross-country convergence:
This graph is more illustrative of the economic links among developing countries since the 1960s.