Proposal from a macroeconomist for an optimal crypto-currency

Dear all,

I'm an academic macroeconomist (with a doctorate, university post etc. for what it's worth). As such, BitCoin and the various other crypto-currencies hold a great deal of interest for me. However, there's something I'd like to discuss with the community, possibly with the ultimate goal of collaborating on a new crypto-currency.

While I have very few doubts that a crypto-currency will come to dominate in the long run, I am somewhat sceptical that it will be any of the current crop, despite Bitcoin's substantial first mover advantage.

Given the constant proliferation of alternate crypto-currencies, it seems likely that in the long-run there will be a range of crypto-currencies all of which use an algorithm without obvious flaws, but which differ in the degree of inflation/deflation and/or price volatility they generate. In such a circumstance, which currency would people pick? Well, the answer to this depends on what the main costs of inflation/deflation are for them.

In standard macro-models today, there are two main costs. Firstly, people face costs due to the necessity of holding cash. If you have to hold cash to make purchases, and that cash is subject to inflation, then the contents of your wallet are constantly losing value -- you are effectively paying a tax to the people creating ("mining") new currency. Secondly, people face costs due to constantly adjusting prices and/or contract terms. For buyers, these costs include search costs, information costs, etc. etc. (If a loaf of bread always costs $1.00 in your normal supermarket, then when you see a loaf of bread on sale for $0.90, you know it's a good deal. If the cost of that loaf of bread is wildly fluctuating in your normal supermarket, then you face a much harder job assessing whether another store's price is a good deal or not.) For sellers, these costs include the cost of going round and physically changing prices in a store, and again various information costs.

Depending on which of these two sets of costs dominate, the exact optimal policy prescription varies, but never by so much. If the former cost dominates, then nominal interest rates should be set to 0 (so steady-state deflation is equal to the real interest rate), meaning there is no opportunity cost of holding cash rather than having your money in a bank. (This is the "Friedman-rule", not to be confused with the "Friedman K% rule", which is not optimal in any standard model.) If the latter cost dominates, then inflation rates should be set to 0.

Directly targeting an inflation rate of 0 to fix the second cost would be very hard with a crypto-currency. Yes, the supply could be controlled to ensure a constant exchange rate to some (basket of) currency(ies), but this would mean putting your trust in the maintenance of the value of the crypto-currency back with national central banks, rather defeating the purpose of using such a crypto-currency in the first place. Even monitoring the relevant inflation rate for a crypto-currency would be difficult, because at present much of their use (if I understand correctly) is in the purchasing of goods where one or both parties don't want it made public that the transaction took place (e.g. because the good is illegal), making it very hard to build a price index.

What about the first cost? Well, first note that with any electronic currency there's no need to set the nominal interest rate to 0 in order to remove the opportunity cost of holding cash. Instead, one can directly pay interest on the currency. With a crypto-currency, this can be done via Peercoin style "proof-of-stake" payments, where the payment rate is tied to the observed risk free nominal interest rate on the crypto-currency (appropriately smoothed). To get this risk free nominal interest rate, the creator of the crypto-currency would create a (ideally, decentralised) platform for the exchange of repurchase agreements denominated in the new currency, using "old" currencies as collateral (though in the long-run, other assets could come to fulfil this role). Although using repurchase agreements rather than unsecured loans removes much of the risk, it may still be desirable to construct a simple reputation system, so that the repo rate for high reputation parties is truly a risk-free rate.

If this is all one did, the interest rate and the inflation rate could be unstable. However, with a crypto-currency one has a second instrument, namely the release of new coins via the "proof-of-work" mechanism. With this one could ensure that the nominal interest rate remained at least (say) 4%, which is approximately the long run real interest rate, meaning that prices would be roughly stable (thus minimising the second cost), and is high enough that any problems stemming from the zero lower bound on nominal interest rates are avoided. In the unlikely scenario in which interest rates actually exceeded 4%, then Peercoin style transaction costs could be applied, though this is to be avoided if at all possible since transaction costs reduce allocative efficiency, having a big welfare cost (and meaning consumers won't be persuaded to use your currency).

Happy to discuss this further if anyone's interested. And if anyone's seriously interested in creating this crypto-currency and wants help, PM me. Another possibility would be open development which seems the best way of avoiding the stink of scammery...

Best regards,

ZeroNominal