only the top 10–20 percent of a typical graduating class of economics PhD students are likely to accumulate a research record that might lead to tenure at a medium-level research university. … graduating from a top department is neither necessary nor sufficient for becoming a successful research economist. Top researchers come from across the ranks of PhD-granting institutions, and lower-ranked departments produce stars with some regularity, although with lower frequency than the higher-ranked departments. Most of the graduates of even the very highest-ranked departments produce little, if any, published research.
The Economist discussed the article here.