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α: calibrated so average coauthorship-adjusted count equals average raw count
One of the most important results of theoretical research on currency systems is that spacing denominations apart by a factor of two is better than a factor of three as this lowers the average number of notes and coins exchanged in transactions. These theoretical studies also claim that an efficient denominational mix has the additional benefit of keeping down the production costs incurred by the central bank. This paper challenges this claim and demonstrates that more efficient currency systems can also be more costly. Central banks therefore face an efficiency-cost trade-off and have to weigh the benefits for transactors against those for the central bank itself.