EONIA stands for Euro OverNight Index Average, and represents the average rate at which banks lend each other money overnight. The function of this overnight lending (and related concepts such as the ECB policy rates, required reserves and maintenance periods) was explained in my first Central Banking 101 post above.

The "EONIA heartbeat" pattern was more clearly seen for a period of 10 months between August 2009 and June 2010 (click the charts to expand):

As we can see from this chart, EONIA stayed roughly constant slightly above the ECB's deposit rate, but spiked on the last day of each ECB reserve maintenance period. The reason for this is that banks incur an opportunity cost for having cash parked as ECB reserves, so normally they keep reserves below their required amount. As the required reserves are computed as a monthly average, on the last day of the reserve maintenance period banks will borrow the funds necessary to meet the reserve requirement. The sudden demand for liquidity raises interbank lending rates, but only for the one day when this liquidity is needed.

The thing is, right after June 2010 the EONIA developed "tachycardia":

I have marked the start of the ECB's bond purchases (Securities Market Purchases, or SMP) on 10 May 2010 because I think it is clear that this is correlated with the start of the tachycardia. The reason is not the bond purchases themselves, which would have naturally improved the liquidity position of European banks, but the fact that the ECB "sterilised" these purchases by draining liquidity from the system in an amount equal to its SMP holdings. The ECB rate raises in mid-2011 visibly didn't help. Personally, I believe Trichet's governing council took these decisions (to sterilize and to raise rates) under pressure from Axel Weber and Jürgen Stark. The rate raises may perhaps be excused by the fact that inflation was trending upwards at the time and the ECB has an idiotically single-minded anti-inflation mandate. However, the sterilization was in my opinion a serious "unforced mistake". I have argued in my previous blogs on this issue that bond purchases don't need to be sterilised and in fact sterilization is contractionary. Here's why.

In 2009, faced with a disintegrating interbank market, the ECB decided to switch its main refinancing operations from "fixed tender" (the ECB would decide the maximum amount of liquidity it was willing to supply, at the target interest rate) to "fixed rate, unlimited tender" (the ECB would lend freely, against eligible collateral, at the reference rate). Now, Eurozone government bonds of the kind the ECB bought in the SMP were eligible collateral for ECB refinancing operations, so after 2009 they could be turned into cash at will (at a small haircut). Now, if you have a bond that you can repo for cash at your sole option, selling it for cash to the ECB really makes little difference to your liquidity position. Therefore, banks which needed liquidity and had SMP-eligible bonds in hand were already likely to be repoing them weekly at the discount window anyway. So the liquidity injected by the ECB through the bond purchases was already in the system.

"Sterilization" means to offer banks to deposit cash with the ECB for a week, at the ECB's reference rate. In this way, an amount of cash equal to the ECB's SMP holdings was withdrawn from the banking system. But as we have argued, this was not extra liquidity that was injected by the SMP: the liquidity was already there. So the net effect of sterilization is to actually decrease system liquidity by the amount of its bond purchases. Therefore, the worse the sovereign debt crisis got, the more liquidity the ECB withdrew, only making matters worse. Then the ECB went and raised rates twice in the middle of a recession responding to cost-push inflation (from commodity imports) and the notional inflationary effects of VAT raises from austerity policies. A wholesale policy disaster, if you ask me.

The EONIA Tachycardia stopped at the end of 2011. This can be seen more clearly by rebasing interest rates around the ECB's reference rate, as in the top half of the following chart:

Nevertheless, as can be seen more clearly in the bottom chart and was noticed by Nordea already six months ago, the EONIA heartbeat has returned. This can only be because the excess liquidity is gone, and the reason is the unwinding (prematurely, in my opinion and based on its effects on EONIA) of the LTRO. Banks have been encouraged to return the 3Y LTRO liquidity a year after it was borrowed. Part of this has been an attempt to signal to "the market" that the health of individual banks was sound, and even that the health of entire national banking systems such as Spain or Italy was good. But already in mid-2013 the EONIA hearbeat returned, and at the end of 2013 SMP sterilization failed a few times.

Failure of SMP sterilization scares de bejeesus out of inflation hawks, but as I argued at the start of 2011 when it happened a couple of times, failures of sterilization indicate that the ECB is trying to drain liquidity that simply isn't there.

So, here we are, three years later liquidity is again so tight that sterilization is failing, and all the hawks can think of is worry that the SMP is becoming "Quantitative Easing through the back door". With such thinking, we have a long crisis ahead of us.