01.10.2020
The role of the European Central Bank's monetary policy in the
COVID-19 crisis
Deusto Business Alumni Meeting
Pablo Hernández de Cos
Governor
Good morning, ladies and gentlemen.
It is a pleasure for me to be able to participate in this meeting organised by Deusto Business
Alumni.
I would like to take this opportunity to share firstly with you some thoughts on how money
monetary policy has helped stave off some of the more serious consequences, at least from
the economic standpoint, of the COVID-19 crisis.
In the second part of my speech, I would also like to reflect on certain challenges that the
gradual reduction in the so-called "natural interest rate" poses for monetary policy conduct
in advanced economies. This is an issue which will be particularly significant in the context
of the monetary policy review initiated at the European Central Bank (ECB).
The monetary policy reaction during the crisis
The outbreak of COVID-19 in Europe in late February and early March was a shock of great
magnitude which triggered an unprecedented economic impact due to the reduction in both
the supply and demand for goods and services. The serious, temporary and global nature
of the shock initially required powerful economic policy actions.
The objective of this "shock therapy" was to avoid a temporary shock from generating
effects which persist over time. Fiscal policy is undoubtedly the most appropriate tool to act
as the first line of defence in this setting, since it has the instruments to achieve this objective
with immediate and targeted actions that are suited to a shock whose duration is uncertain
and heterogeneous.
The response of European governments has generally been commensurate with the
challenges posed by this crisis. Their response has also been resolutely backed by the
European Union (EU), especially following the approval of the European Recovery Fund by
the European Council.
For its part, monetary policy should act, and has acted, very forcefully too. Indeed, the
economic shock triggered by the pandemic was accompanied by aa strong tightening of
financial conditions in the euro area. As various governments, including Spain's, announced
plans to contain the virus, financial markets began to discount heavy declines in economic
activity and increases in public and private debt.
This drove risk premia (i.e. the compensation demanded by bond investors for the
probability of borrowers defaulting) higher. That resulted in an increase in the interest rate
that governments, households and firms pay on their rising debts, which will necessarily
amplify the fall in aggregate demand and, therefore, in inflation, owing to the direct impact
of the pandemic and the measures adopted to limit its spread.
Faced with this situation, on the ECB Governing Council we had to act swiftly to reverse the
upswing in the borrowing costs for the various economic agents. This was the only way to
avoid a sharp tightening in capital markets which, with all certainty, would have fuelled a
greater economic contraction and, possibly, a deflationary scenario.
A specific additional problem of the euro area was the so-called "fragmentation" in the
transmission of the common monetary policy. This means that the financing conditions of
governments, and also of firms and financial institutions, vary significantly across countries,
as a result, among other factors, of the different sovereign risk premia in the euro area. In
fact, the cost of government debt in each country usually acts as a "floor" or "baseline" for
corporate and bank debt. Consequently, in those countries whose governments have a
better outlook for the repayment of their debt and, consequently, which have more
favourable financing conditions, the borrowing costs of firms and households, through bank
credit, will be lower.
The initial phase of the COVID-19 crisis had an asymmetrical effect on euro area countries.
This meant that certain countries, such as Italy and Spain, which already had substantially
high levels of public debt, were hit harder by the first wave of the virus both epidemiologically
and in terms of their reliance on more vulnerable industries such as tourism and hospitality.
Borrowing costs duly rose much more markedly in these countries.
Faced with this situation, the ECB Governing Council decided to announce new monetary
policy measures with the dual n objective of reducing fragmentation and increasing the
accommodative stance of monetary policy. For this reason, we adopted two types of
measures.
First, we announced the implementation of the Pandemic Emergency Purchase Programme
(PEPP). This programme, with an initial envelope of €750 billion, which was subsequently
increased to €1.35 trillion until June 2021, permits the ECB to purchase government and
private sector bonds, as well as other debt instruments.
The ECB already had a purchase programme, the APP, which increased in volume at the
onset of the crisis. Why did it then need a second programme? The APP has a relatively
rigid structure regarding the distribution of asset purchases both over time and by
jurisdiction.
In the latter case, APP purchases are distributed under the so-called "capital key", a
concept referring to the percentage of the ECB's capital held by each national central bank,
which is linked to the weight of each country's economy and population.
However, faced with an emergency such as that in March, the ECB had to be able to buy
proportionally more bonds from some countries than others so that it could concentrate
those purchases on countries whose financing conditions, at any given time, were subject
to a greater degree of tightening. The PEPP was designed precisely with that degree of
flexibility in the distribution of asset purchases over time and by geographical area, although
the capital key continued to act as a guide for the latter.
It was probably thanks to this flexibility, together with the large volume of asset purchases
initially envisaged, that the announcement of the creation of the PEPP on 18 March served
to substantially reduce interest rates on sovereign debt - especially that of countries at that
time more harshly affected by the health crisis, such as Italy and Spain - and consequently,
those on bank and corporate debt.
To sum up, the PEPP cut short the downturn in euro area financial markets and gave way
to the process of gradual easing of financial conditions which has continued up until the
present day. This easing was essential for providing fiscal authorities in all countries in the
area with room for manoeuvre, which has allowed them to deploy unprecedented measures
to sustain the income of households and firms.
Looking ahead, and without detriment to the use of the capital key as a guide for the
distribution of asset purchases, the ECB has reiterated its willingness to continue to tailor
the volume, composition and type of these purchase to the developments in economic and
financial conditions in the euro area.
Secondly, we introduced a series of measures aimed at smoothing bank lending in the
context of the COVID-19 crisis. In the euro area, banks are the main source of financing for
households, the self-employed and firms (especially SMEs). It was thus vital to prevent a
severe contraction in the flow of credit to the real economy.
The risk of such a contraction stemmed mainly from two factors: on one hand, the possibility
that money markets would deteriorate to the point of compromising banks' access to them;
and, on the other, the possible reluctance of banks to take on fresh risks in the form of loans
against a background of enormous economic uncertainty.
To address the first of these risks, the ECB launched a series of longer-term refinancing
operations (LTROs). These provided banks with "bridge financing" under advantageous
conditions until late July, for when a substantial tender I shall now refer to was scheduled.
That stabilised funding costs for the banking sector at a juncture, as I stated, of great
uncertainty.
As to the second risk, namely banks' reluctance to extend new loans in such a complex
economic environment, the ECB already had an instrument to encourage banks to provide
credit: the so-called "targeted longer-term refinancing operations" (TLTRO-III).
This programme affords banks financing under particularly advantageous conditions,
provided they meet certain lending targets to households and firms (excluding, in the former
case, lending for house purchases). With the onset of the pandemic, this programme was
modified to make it more attractive to banks, enabling them to obtain funding temporarily
at an interest rates as low as -1%, under the condition of not reducing their eligible volume
of credit.
To obtain liquidity in the Eurosystem's refinancing operations, including TLTRO-III,
participating banks must nevertheless pledge collateral in order to protect the Eurosystem
from potential bank failures. Hence, and to help banks obtain the biggest amount of
financing possible in these operations, the ECB relaxed its collateral framework conditions.
For instance, it reduced the average haircut applied to collateral assets and accepted riskier
assets and, most especially, loans backed by the national authorities' various programmes,
such as the ICO (Official Credit Institute) guarantees in Spain's case. As a result, commercial
banks could increase the liquidity they obtained from the Eurosystem by using their loans
to the real economy as collateral.
The combination of these measures was successful. The weekly LTRO operations provided
substantial amounts of liquidity to banks during the most difficult months of the pandemic.
In the June TLTRO-III operation, participating banks received a total of €1.31 trillion, a record
high in Eurosystem refinancing operations.
All these operations played a vital role in preserving the supply of bank lending in the euro
area. They contributed to the momentum shown by the new refinancing operations -
particularly in the case of lending targeted on firms and the self-employed - from the outset
of the pandemic, and they kept interest rates on loans at record lows.
The complementarity of these measures and those adopted by national governments (in
particular through the public loan-guarantee programmes) and by the macro- and
microprudential authorities (which enable financial institutions, for example, to use some of
the capital buffers built up in recent years) has been pivotal in providing for the flow of
financing in the economy during the crisis.
Beyond their impact on the financing conditions for households, firms and Governments,
we should assess whether all these measures have achieved their ultimate goal. This is none
other than supporting euro area economic growth and, thereby, helping inflation adjust
towards its medium-term objective, in keeping with the ECB's price stability mandate,
namely inflation below, but close to, 2%.
Preliminary Banco de España estimates suggest that the PEPP would have an impact of the
highest order on inflation and on the GDP growth rate, in both the euro area as a whole and
in Spain. Indeed, the cumulative impact on GDP growth is expected to be somewhat greater
in the case of the Spanish economy. However, it is difficult to quantify the financial and
economic damage there would have been had the PEPP not been implemented. One of the
main effects of monetary policy decisions, in a setting as complex as that which was in
place at the outset of this crisis, is to prevent financial market disruption that may ultimately
lead to deeper and more persistent economic crises.1
Where are we at present?
Evidently, it is too soon to say the COVID-19 economic crisis is over. Admittedly, economic
activity is rebounding in the third quarter, following an unprecedented decline in euro area
GDP in the second quarter. This still-partial recovery is highly uneven across both regions
and sectors of activity. It is moreover fragile, since the lockdown-easing measures are being
accompanied by an increase in infections in some countries. That, in turn, has begun to
require the re-introduction of measures in some countries that enable the speed of
contagion to be curtailed at the cost of setting certain limits on activity. In fact, the latest
economic indicators, such as the PMI and the European Commission's business sentiment
index, showed some slowing in activity in August following the rebound in July. As a result,
the recovery is subject to enormous uncertainty.
All told, activity in the third quarter is expected to recoup in part the heavy loss of output in
the second quarter. Overall euro area growth could thus stand at around 8.4%.
For the year as a whole, the ECB's September macroeconomic projections show, in the
baseline scenario, an 8% decline in GDP in 2020 (slightly less sharp than what was expected
in June). The economy is expected to pick up as from the third quarter of this year, with
increases of 5% in 2021 and 3.2% in 2022, although the pre-crisis GDP level would not be
attained until the end of the projection period. Nonetheless, euro area GDP is expected, at
end-2022, to still be somewhat less than 4 pp below the level that would have been
observed according to last year's December projections (the latest before the COVID-19
outbreak).
Given the exceptional uncertainty over future pandemic-related developments, this baseline
scenario has been accompanied by a more favourably defined alternative scenario. In it,
euro area GDP would, at the end of the time horizon considered, be slightly higher than was
envisaged in December 2019. Another, more adverse scenario was also laid down, in which
the negative gap relative to the 2019 reference would be around 9 pp.
Inflation fell in August to - 0.2%, and its core component, which excludes energy and food,
stood at a very low level of 0.4%. The ECB's projections point to a gradual recovery in the
coming years. At the end of the projection horizon, inflation would stand at only 1.3%, some
distance off our related target.
Moreover, several factors tilt the risks to economic growth to the downside: uncertainty over
how the pandemic will evolve; the possibility of a no-deal Brexit; and a potentially more
adverse reaction by unemployment and in the dynamics of corporate start-ups and
company failures once the support measures have run their course.
In parallel, there has been a progressive appreciation by the euro in recent months. This
introduces disinflationary pressures at a time when the euro area inflation outlook is, as I
said, for a record low. Accordingly, on the ECB Governing Council we have reiterated that
we will closely monitor the exchange rate.
In short, the fragility of the recovery in the euro area, a medium-term inflation forecast far
below our objective and a nominal effective exchange rate that has in recent months
countered much of our stimulus all lead to the conclusion that there is no room for
complacency. We should retain a significant monetary stimulus until we have a sound
recovery in place. Moreover, we stand ready to recalibrate the foregoing measures, or to
introduce new ones were it necessary, to fulfil our price stability mandate, understandably
always in a symmetrical manner. It is also crucial to retain flexibility in the application of our
asset purchase programmes to head off potential financial fragmentation problems.
The other national and European economic authorities must appreciate that, given the
uncertainty over the future course of the pandemic and, therefore, over the soundness of
the economic recovery, it is essential they maintain their stimulus measures, now in a more
selective and targeted fashion. An early withdrawal of these measures would harm the euro
area productive system and, potentially, our financial system. The extent of such harm
would exceed the potential medium-term costs of retaining the measures over time. And
depending on how the pandemic and its economic impact evolve, it cannot be ruled out
that such measures may need to be expanded.
Defining price stability in the context of low natural interest rates
In the second part of my address I will take a longer-term perspective and reflect on the
changes occurring in the implementation of monetary policy in the advanced economies.
In the years prior to the 2007-2012 crisis, which in our case coincided with the early years
of the ECB, a certain consensus emerged among the advanced economies regarding the
role and functioning of central banks. These were designed as independent entities, that is,
not subject to direct control by governments, with a clear mandate to ensure stable prices,
and also in some jurisdictions, such as the United States, full employment.
The price stability mandate is normally articulated as a numerical inflation objective,
frequently 2% or, as in the case of the ECB, a level below but close to 2%. To achieve its
price stability target, the central bank adjusts the general level of interest rates on the
funding raised - via bank loans or in the debt markets - by agents in the real economy
(businesses, households and governments).
Although the central bank controls the nominal interest rate, it is the "real" interest rate -
that is, the nominal rate less expected inflation - that is relevant for households' and
businesses' spending decisions. For instance, a nominal interest rate of 2% when expected
inflation is 4% is much more expansive than a nominal interest rate of 1% in a
noninflationary setting.
Given that the prices that determine inflation are partly rigid, the central bank may influence
the real interest rate by adjusting nominal rates. Before the onset of the financial crisis, the
central bankers' manual prescribed that if the economy is overheating and prices and wages
are under growing pressure, the central bank should raise nominal interest rates above
inflation expectations, thus tightening real rates and cooling down the economy. And vice
versa, in a downturn, with falling prices and rising unemployment, the central bank should
cut nominal interest rates, thus reducing real rates and stimulating aggregate demand.
Conceptually, central bankers sought to maintain real interest rates at a level - known as
the natural rate of interest - that would hold GDP at its potential level and would keep
inflation stable around its target level.2 This natural rate of interest is not directly observable
and may only be estimated, with some degree of uncertainty, using econometric
techniques.3
In recent decades this natural rate of interest has gradually fallen in the advanced
economies. This is attributed both to demographic factors (such as population ageing) and
to technological factors (such as low productivity growth), which have changed the balance
between the supply of savings and the demand for investment.
In consequence, to stabilise inflation, real interest rates must now be lower than they were
two or three decades ago. Indeed, in economies such as the euro area, various estimates
even place the natural rate of interest at negative levels.4 This would not be a problem if
nominal rates were able to fall as far as was necessary; for example, with expected inflation
of 1%, to place the natural rate of interest at, let's say, -2%, the nominal rate would have to
be lowered to -1%.
The problem lies in the fact that nominal interest rates cannot fall as far as is necessary into
negative territory. If the central bank were to impose negative rates of -5%, for example, the
commercial banks would bear negative returns on the bulk of their assets. This would
adversely affect their financial intermediation capacity, with a consequent negative impact
on the supply of credit, economic activity and inflation.
There is therefore a lower bound on nominal interest rates: if the central bank reduces
interest rates below that level, the effect on the economy may be contractionary rather than
expansionary, owing to the negative impact on the financial system overall.5 The level of
that lower bound on interest rates is not directly observable and varies over time in
accordance with the situation of the financial sector. However, it is, in any event, the lower
limit on the extent to which central banks may reduce interest rates.
In Europe, the ECB's deposit facility rate was already at -0.5%, even before the onset of the
COVID-19 crisis.6 Although the door is still open for future additional cuts in this interest
rate, it seems evident that in the present circumstances there is relatively limited room for
manoeuvre for conventional monetary policy, i.e. monetary policy based on controlling
interest rates in the short term.
The lower bound on interest rates introduces asymmetry into the way in which central banks
implement monetary policy. As I mentioned earlier, if inflation rises above its target level,
central banks may raise interest rates as far as is necessary to "cool down" the economy.
However, when faced with deflationary shocks that take inflation below the target level and
require that central banks lower their interest rates, these may ultimately "hit" the lower
bound. This asymmetry means that monetary policy is potentially highly effective in
combating inflation, but less so in combating deflation or even persistently low inflation.
This last factor may create a dangerous vicious circle. Against a backdrop in which it is
expected that the lower interest rate bound may frequently limit central banks' capacity to
act, economic agents will expect that any inflation deviations above the target level will be
swiftly corrected. But not deviations below the target level. In consequence, expected
inflation, in terms of the average over a broad period, will tend to move below the target
level. Given that in the long run, the nominal interest rate is the real equilibrium rate plus
expected inflation, any fall in the latter implies lower nominal rates on average, which means
that these will hit their lower bound more frequently. All the above implies less headroom
for providing stimulus measures in downturns marked by low inflation. This in turn leads to
lower inflation expectations, and thus it continues.
Asset purchase programmes, such as the ECB's APP and PEPP, are an attempt to break
out of this vicious circle. These programmes are conducive to lower interest rates on
medium and long-term public and private-sector bonds. In this way, although short-term
interest rates are limited by the lower bound, the ECB is able to reduce longer-term interest
rates, which are often the most relevant rates for determining economic agents' spending
decisions. This is what is known as "flattening the yield curve".
Similarly, bank refinancing operations, such as the TLTROs, can reduce banks' funding
costs and, ultimately, the cost of bank loans, thus stimulating aggregate demand and
inflation.7
However, even though these measures have been highly effective in the euro area in present
and recent circumstances, they do not completely eliminate the limits on the degree of
potential monetary stimulus deriving from the existence of the lower interest rate bound. In
consequence, central banks have introduced other tools with which to smooth that limit, the
most common of these being forward guidance.8
This enables the central bank to offer guidance to the market as to how interest rates will
evolve, or are expected to evolve, in future. For instance, in its monetary policy
announcements, the ECB links the question of holding its interest rates at their present
levels, or lower, to inflation developments in the euro area. In this manner, the ECB seeks
to convey to financial markets, and to society at large, the conditions that would have to be
met in order to begin to raise interest rates.
Where short-term interest rates are close to their lower bound, forward guidance may
stimulate the economy insofar as the central bank undertakes in a credible manner to
tolerate inflation over the target level once the economic situation thus permits.9
Given that the real interest rate is the nominal rate stripping out inflation expectations, if the
central bank is able to raise these expectations, it can reduce the real interest rate today,
even if nominal rates remain constant. The problem is that that commitment means that the
central bank is voluntarily breaching its future inflation objective, which may possibly not be
credible in advance.
This is what we economists call "dynamic inconsistency": a central bank could announce
today that it will tolerate higher inflation in future in order to stimulate the economy, but once
the economy and inflation recover, there would be an incentive for it to breach its initial
announcement if it conflicted with its price stability objective. If agents doubt the central
bank's credibility, this type of forward guidance will not be effective in the first place.
One way to avoid this problem is by modifying the monetary policy "strategy", seeking to
grant greater credibility and transparency to the central bank's actions; in other words, to
change the way in which the central bank's objective is articulated and the way that the
central bank pursues that objective with the tools available. To date, in their strategic
frameworks most central banks have followed variations of inflation targeting, which entails
targeting an inflation rate that is close to a specific number (for example, 2%) over a
medium-term horizon.
There are however alternative monetary policy strategies that automatically generate similar
dynamics to those of the forward guidance described above. These are the so-called
makeup strategies,10 one of which is price-level targeting.
In this case, the central bank announces a target growth rate for the price level (for example,
of 2%). Unlike in the case of inflation targeting, if for some reason inflation stands
temporarily below 2%, the central bank will have to ensure that it rises above 2% in the
future in order to ensure that the price level returns to its target path. In a way, this strategy
obliges the central bank to correct in future any past deviation of inflation consistent with its
medium-term target.
A less radical strategy, albeit similar in spirit, is known as average inflation targeting". In this
case, the central bank attempts to keep average inflation at its target level over a certain
timeframe. Unlike traditional inflation targeting, it includes an element of compensation for
past deviations, although this is limited in time. Under price level targeting, in contrast, all
past deviations must be compensated, irrespective of the time that has elapsed since they
occurred.
One problem with these compensation strategies is their symmetry, understood as the
central bank's commitment to react equally to below-target inflation deviations (which, as
we have seen, are the really problematic ones in the current setting) and above-target
deviations; i.e., following a period of above target inflation, the central bank would have to
reduce inflation below the target, which would require depressing economic activity and
employment.
Given that a commitment of this type may not be fully credible, it has recently been
proposed that these strategies should be temporary: the central bank would normally
operate under a traditional inflation targeting regime, but, in the event of a crisis with low
inflation and interest rates close to the lower bound, the strategy would be to compensate
in future for the "lost inflation" in this period.11
In recent years, various central banks have initiated monetary policy strategy reviews
(including the ECB and the US Federal Reserve). In fact, the Federal Reserve has recently
announced the main results of its strategic review, which, among other changes, has led to
the adoption of a new average inflation targeting strategy, albeit with an undefined
timeframe for calculating the average inflation that is to be stabilised.
In particular, the Federal Reserve states that, under its new strategic framework, when
inflation stands persistently below 2% it will attempt to keep inflation moderately above 2%
for a certain time.12
With regard to the ECB, in January this year it announced the launch of a review of its
monetary policy strategy. This review has been delayed by the emergence of COVID-19 and
is expected to extend into next year. Since this review is ongoing we still do not know what
its conclusions will be, but I can confirm that this is an open process: both the ECB and the
Eurosystem national central banks are performing a large amount of analysis and requesting
the opinion of civil society, academic economists and other professional and social groups.
One of the key aspects of this review will be the definition of price stability. The current
inflation objective, consisting of rates below, but close to, 2%, may be reformulated. On one
hand, it may be necessary to clarify the specific level of inflation that is targeted, in order to
make it easier for economic agents to understand. On the other hand, in line with my
comments above, this objective could be made more symmetric, by clarifying that the
degree of tolerance of above-target inflation deviations is the same as for below-target
deviations.13 Also, in the current low inflation environment, with interest rates close to their
lower bound, the inflation target should take into account the need for a sufficiently large
buffer above zero, to provide more scope for conventional interest-rate policy.
Irrespective of the final outcome, I am sure that the result of this review will strengthen the
effectiveness of monetary policy in the euro area and its capacity to achieve its aims in the
macroeconomic environment of the coming decade.
I should like to conclude with a final reflection on the interaction between monetary and
fiscal policy going forward. Experience in recent years suggests that appropriate interaction
between these policies may decisively contribute to each of them achieving their objectives
more efficiently.
As I have attempted to emphasise, the ECB's monetary policy action in response to the
economic consequences of the pandemic has been rapid and decisive. Moreover, we are
prepared to add further monetary stimulus, if necessary. Fiscal policy action has also been
forceful. It is important that this action be maintained during the recovery, in a more focused
way, and, if necessary, even increased. This is particularly true for European policy, in the
context, for example, of the recently approved European recovery fund (Next Generation
EU).14 The spending and investment arising from the use of this fund for projects capable of
transforming our economies and for financing reforms to raise their sustainable growth
capacity, will be fundamental to consolidate the economic recovery and reduce the
potentially permanent consequences of the crisis. More in the medium term, it is crucial that
this fund be converted into a permanent, common fiscal stabilisation instrument for the euro
area. This would allow a joint fiscal response to macroeconomic shocks and provide a larger
supply of safe European assets, facilitating the general functioning of financial markets and
the specific conduct of monetary policy.
References
Aguilar, P., Ó. Arce, S. Hurtado, J. Martínez-Martín, G. Nuño and C. Thomas (2020). "La
respuesta de la política monetaria del BCE frente a la crisis del COVID-19", Occasional
Paper, Banco de España, forthcoming.
Andreeva, D. and M. García-Posada (2019). The impact of the ECB ́s targeted long-term
refinancing operations on banks' lending policies: the role of competition, Working Paper
No. 1903, Banco de España.
Arce, Ó., R. Gimeno and S. Mayordomo (2017). Making room for the needy: the
creditreallocation effects of the ECB's corporate QE, Working Paper No 1743, Banco de España,
forthcoming in Review of Finance.
Arce, Ó., I. Kataryniuk, P. Marín and J. J. Pérez (2020). Thoughts on the design of a European
Recovery Fund, Occasional Paper No 2014, Banco de España.
Arce, Ó., M. García-Posada, S. Mayordomo and S. Ongena (2018). Adapting lending policies
when negative interest rates hit banks' profits, Working Paper No 1832, Banco de España.
Arce, Ó., G. Nuño and C. Thomas (2019). "The Eurosystem's monetary policy following the
end of net asset purchases", Analytical Articles, Economic Bulletin 1/2019, Banco de
España.
Bernanke, B. S., M. T. Kiley and J. M. Roberts (2019). "Monetary Policy Strategies for a
LowRate Environment", AEA Papers and Proceedings, No 109, pp. 421-426.
Brunnermeier, M. K., and Y. Koby (2018). The Reversal Interest Rate, NBER Working Paper,
No 25406.
Eggertsson, G. and M. Wood