I think the point of publication bias is very important. In fact, in our paper we document that the top-5 economic journals publish papers from the U.S. a lot more than those from other countries. However, for the entire body of economic research, we looked at the top 200 economics journals. Among these, the last 80 have a 0 citation count, suggesting that publication bias may not be as big a concern. At the same time, as we note in the paper, these numbers exclude reports, books and journals like the Economic and Political Weekly in India, which are all important outlets for research. The key question I think is whether publication in these other outlets is a substitute or a complement to publication in the top-200 economics journals, and my sense is the latter. That is, I think that the ratio of research in these journals to the total body of research is pretty similar and perhaps even declining with country income. This however, is based entirely on observation and not data--so would love to see what it actually looks like.