Just as trade is more likely to occur between parties less geographically distant, the same appears to be true for communication. In the U.S. telephone network about 1983, the share of calls within the local switching office averaged 66% for rural switching offices, compared to 31% for urban switching offices. The greater share of intra-office calls in rural switching offices occurred despite rural offices serving on average only 700 telephone lines, compared to 41,000 telephone lines for urban offices. The relevant difference seems to be geographic distance: rural offices served on average 130 square miles, while urban offices averaged 12 square miles of service area. Geographic distance shaped calling patterns much more than the number of persons that could be called.
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Data: switching-center statistics for the U.S. public telephone network, c. 1983 (Excel version)
