We address the fundamental question arising in economic geography: why do economic activities agglomerate in a small number of places? The main reasons for the formation of economic clusters involving firms and/or households are analysed: (i) externalities under perfect competition; (ii)...

Paul Krugman has clarified the microeconomic underpinnings of both spatial economic agglomerations and regional imbalances at national and international levels. He has achieved this with a series of remarkably original papers and books that succeed in combining imperfect competition, increasing...