%X The size distribution of business firms is explained using number and size of firms' constituent components. It is a lognormal distribution multiplied by a stretching factor which can lead to a Pareto upper tail. This result is confirmed empirically. %L eprints638 %D 2008 %A Fabio Pammolli %A Jakub Growiec %A Massimo Riccaboni %A H. Eugene Stanley %K Tail behavior; Firm size distribution; Gibrat Law; Pareto distribution; Lognormal distribution %N 2 %R 10.1016/j.econlet.2007.04.031 %J Economics Letters %P 207 - 212 %T On the size distribution of business firms %I Elsevier %V 98 %O JEL classification codes: L11; L65