A 1931 statistical law explains why a few giant firms dominate every industry

French economist Robert Gibrat found in 1931 that a firm's percentage growth rate in any year has nothing to do with its current size — tiny and huge firms grow by similarly random percentage shocks. Run that process forward and it produces a hugely skewed, long-tailed spread of firm sizes by chance alone, no superior management required. It remains one of the earliest statistical explanations for why most industries end up dominated by a handful of giants.

— Robert Gibrat, Les Inegalites economiques — 1931; formalized as the 'law of proportionate effect'