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A blog on financial markets and their regulation
A few days back, the IMF made a change in its rule for setting interest rates on SDRs (Special Drawing Rights) and set a floor of 5 basis points (0.05%) on this rate. The usual zero lower bound on interest rates does not apply to the SDR as there are no SDR currency notes floating around. The SDR is only a unit of account and to some extent a book entry currency. There is no technical problem with setting the interest rate on the SDR to a substantially negative number like -20%.
In finance theory, there is no conceptual problem with a large negative interest rate. Though we often describe the interest rate (r) as a price, actually it is 1+r and not r itself that is a price. The price of one unit of money a year later in terms of money today is 1+r. Prices have to be non negative, but this only requires that r can not drop below -100%. With bearer currency in circulation, a zero lower bound (ZLB) comes about because savers have the choice of saving in the form of currency and earning a zero interest rate. Actually the return on cash is slightly negative (probably close to -0.5%) because of storage (and insurance) costs. As such, the ZLB is actually not at zero, but at somewhere between -0.25% and -0.50%.
It has long been understood that a book entry (or mere unit of account) currency like the SDR is not subject to the ZLB at all. Buiter for example proposed the use of a parallel electronic currency as a way around the ZLB.
In this context, it is unfortunate that the IMF has succumbed to the fetishism of positive interest rates. At the very least, it has surrendered its potential for thought leadership. At worst, the IMF has shown that it is run by creditor nations seeking to earn a positive return on their savings when the fundamentals do not justify such a return.