Ancient coin designs encoded increasing amounts of economic information over centuries

Barbara Pavlek,James Winters,Olivier Morin

doi:10.1016/j.jaa.2019.101103

Abstract

Coinage, the practice of minting small bits of metal with distinctive marks, appearing in the second half of the 7th century BCE, had a transformative impact upon ancient economies and societies. Controversies endure concerning the original function of ancient coinage, in particular the respective role of states and markets in its emergence. Applying information-theoretic measures to a corpus of 6859 distinct coin types from the Ancient Mediterranean world, dated between c. 625 and c. 31 BCE, we show that the symbols minted on coins (designs combining images of plants, deities, animals, etc.) became increasingly informative about a coin’s value. This trend was specific to value-relevant information, as distinct from information concerning issuing states. Coin designs also carried more information about higher denominations than about lower ones. Before numerical or written marks of value became widely used on coinage, these iconic symbols were carrying economic information.

Highlights

One arresting feature of cultural evolution is information growth (Hidalgo, 2015; Morris, 2013): the capacity of human societies to store and manipulate information has increased by orders of magnitude over the course of human history
When testing the chronological predictions, the coin types were arranged by approximate date, into 18 “date bins”, each dated by their median year
We found a significant drop in state-relevant information with time: the conditional entropy of authorities given designs becomes higher with time, corresponding to a decrease in informational value (Spearman’s ρ = 0.529, p = 0.026)

Summary

Introduction

One arresting feature of cultural evolution is information growth (Hidalgo, 2015; Morris, 2013): the capacity of human societies to store and manipulate information has increased by orders of magnitude over the course of human history. Key to this trend is our growing ability to store and manipulate information on economic transactions. The second solution consists in exchanging tokens of value, such as coins In the latter case, no record of the transaction needs to be produced or kept: one agent gains tokens of value that used to belong to another agent. The distribution of tokens of value among agents in a market can record vital economic information, in a decentralized way (Hayek, 1945), lowering transaction costs (Bresson, 2009)

Objectives

Results

Conclusion