It has become customary that commissions of experts meet to reply to questions like the following: what will be the population of the country, or even of our planet,1 in 10, 15 or 25 years, or indeed at the end of the century? What will be its composition in age categories, its regional distribution, its concentration of urban agglomerations? In what proportion will production have increased, what modifications will its composition and utilizations have undergone? How will the consumption of energy have been augmented, and in what forms? And equally for raw materials: where will these natural resources be obtained, and with what changes in the channels of trade?