UC Irvine

Several rational models are constructed to show why the ratio of a country's foreign trade to its GNP should decrease with increasing country size. A physics-inspired model of absorption of a quasi-continuous particle flow by a quasi-homogeneous space results in detailed agreement with the observed contemporary world-wide pattern of import/GNP vs. population size. On the average, world imports behave as if 63% of a product flow were absorbed by the nearest 730,000 people or by people within 37 miles of the production center, whichever number of people is higher. "Characteristic transport distances" (over which 63% of flow is absorbed) are given for 110 countries and range from 10 to 300 miles. The corresponding "characteristic absorption numbers" range from 160 to 1700 people; they indicate the number of people, linearly arranged, which absorbs 63% of a flow. © 1976.