Saturday Quiz – September 24, 2011 – answers and discussion

Here are the answers with discussion for yesterday’s quiz. The information provided should help you work out why you missed a question or three! If you haven’t already done the Quiz from yesterday then have a go at it before you read the answers. I hope this helps you develop an understanding of Modern Monetary Theory (MMT) and its application to macroeconomic thinking. Comments as usual welcome, especially if I have made an error.

Question 1:

Assume that a nation is continuously running an external deficit of 2 per cent of GDP. If the private domestic sector successfully spends less than its income, then we would always find a public sector deficit.

The answer is True.

This question requires an understanding of the sectoral balances that can be derived from the National Accounts. But it also requires some understanding of the behavioural relationships within and between these sectors which generate the outcomes that are captured in the National Accounts and summarised by the sectoral balances.

Refreshing the balances (again) – we know that from an accounting sense, if the external sector overall is in deficit, then it is impossible for both the private domestic sector and government sector to run surpluses. One of those two has to also be in deficit to satisfy the accounting rules.

The important point is to understand what behaviour and economic adjustments drive these outcomes.

So here is the accounting (again). The basic income-expenditure model in macroeconomics can be viewed in (at least) two ways: (a) from the perspective of the sources of spending; and (b) from the perspective of the uses of the income produced. Bringing these two perspectives (of the same thing) together generates the sectoral balances.

From the sources perspective we write:

GDP = C + I + G + (X – M)

which says that total national income (GDP) is the sum of total final consumption spending (C), total private investment (I), total government spending (G) and net exports (X – M).

From the uses perspective, national income (GDP) can be used for:

GDP = C + S + T

which says that GDP (income) ultimately comes back to households who consume (C), save (S) or pay taxes (T) with it once all the distributions are made.

Equating these two perspectives we get:

C + S + T = GDP = C + I + G + (X – M)

So after simplification (but obeying the equation) we get the sectoral balances view of the national accounts.

(I – S) + (G – T) + (X – M) = 0

That is the three balances have to sum to zero. The sectoral balances derived are:

• The private domestic balance (I – S) – positive if in deficit, negative if in surplus.
• The Budget Deficit (G – T) – negative if in surplus, positive if in deficit.
• The Current Account balance (X – M) – positive if in surplus, negative if in deficit.

These balances are usually expressed as a per cent of GDP but that doesn’t alter the accounting rules that they sum to zero, it just means the balance to GDP ratios sum to zero.

A simplification is to add (I – S) + (X – M) and call it the non-government sector. Then you get the basic result that the government balance equals exactly $-for-$ (absolutely or as a per cent of GDP) the non-government balance (the sum of the private domestic and external balances).

This is also a basic rule derived from the national accounts and has to apply at all times.

So what economic behaviour might lead to the outcome specified in the question?

If the nation is running an external deficit it means that the contribution to aggregate demand from the external sector is negative – that is net drain of spending – dragging output down. The reference to the specific 2 per cent of GDP figure was to place doubt in your mind. In fact, it doesn’t matter how large or small the external deficit is for this question.

Assume, now that the private domestic sector (households and firms) seeks to increase its saving ratio and is successful in doing so. Consistent with this aspiration, households may cut back on consumption spending and save more out of disposable income. The immediate impact is that aggregate demand will fall and inventories will start to increase beyond the desired level of the firms.

The firms will soon react to the increased inventory holding costs and will start to cut back production. How quickly this happens depends on a number of factors including the pace and magnitude of the initial demand contraction. But if the households persist in trying to save more and consumption continues to lag, then soon enough the economy starts to contract – output, employment and income all fall.

The initial contraction in consumption multiplies through the expenditure system as workers who are laid off also lose income and their spending declines. This leads to further contractions.

The declining income leads to a number of consequences. Net exports improve as imports fall (less income) but the question clearly assumes that the external sector remains in deficit. Total saving actually starts to decline as income falls as does induced consumption.

So the initial discretionary decline in consumption is supplemented by the induced consumption falls driven by the multiplier process.

The decline in income then stifles firms’ investment plans – they become pessimistic of the chances of realising the output derived from augmented capacity and so aggregate demand plunges further. Both these effects push the private domestic balance further towards and eventually into surplus

With the economy in decline, tax revenue falls and welfare payments rise which push the public budget balance towards and eventually into deficit via the automatic stabilisers.

If the private sector persists in trying to increase its saving ratio then the contracting income will clearly push the budget into deficit.

So if there is an external deficit and the private domestic sector saves (a surplus) then there will always be a budget deficit. The higher the private saving, the larger the deficit.

The following Graph and related Table shows you the sectoral balances written as (G-T) = (S-I) – (X-M) and how the budget deficit rises as the private domestic saving rises.

The following blogs may be of further interest to you:

• Barnaby, better to walk before we run
• Stock-flow consistent macro models
• Norway and sectoral balances
• The OECD is at it again!

Question 2:

If economy-wide average nominal wages grow more slowly than the inflation rate then real income is being redistributed to profits.

The answer is False.

The wage share in nominal GDP is expressed as the total wage bill as a percentage of nominal GDP. Economists differentiate between nominal GDP ($GDP), which is total output produced at market prices and real GDP (GDP), which is the actual physical equivalent of the nominal GDP. We will come back to that distinction soon.

To compute the wage share we need to consider total labour costs in production and the flow of production ($GDP) each period.

Employment (L) is a stock and is measured in persons (averaged over some period like a month or a quarter or a year.

The wage bill is a flow and is the product of total employment (L) and the average nominal wage (w) prevailing at any point in time. Stocks (L) become flows if it is multiplied by a flow variable (W). So the wage bill is the total labour costs in production per period.

So the wage bill = W.L

The wage share is just the total labour costs expressed as a proportion of $GDP – (W.L)/$GDP in nominal terms, usually expressed as a percentage. We can actually break this down further.

Labour productivity (LP) is the units of real GDP per person employed per period. Using the symbols already defined this can be written as:

LP = GDP/L

so it tells us what real output (GDP) each labour unit that is added to production produces on average.

We can also define another term that is regularly used in the media – the real wage – which is the purchasing power equivalent on the nominal wage that workers get paid each period. To compute the real wage we need to consider two variables: (a) the nominal wage (W) and the aggregate price level (P).

We might consider the aggregate price level to be measured by the consumer price index (CPI) although there are huge debates about that. But in a sense, this macroeconomic price level doesn’t exist but represents some abstract measure of the general movement in all prices in the economy.

Macroeconomics is hard to learn because it involves these abstract variables that are never observed – like the price level, like “the interest rate” etc. They are just stylisations of the general tendency of all the different prices and interest rates.

Now the nominal wage (W) – that is paid by employers to workers is determined in the labour market – by the contract of employment between the worker and the employer. The price level (P) is determined in the goods market – by the interaction of total supply of output and aggregate demand for that output although there are complex models of firm price setting that use cost-plus mark-up formulas with demand just determining volume sold. We shouldn’t get into those debates here.

The inflation rate is just the continuous growth in the price level (P). A once-off adjustment in the price level is not considered by economists to constitute inflation.

So the real wage (w) tells us what volume of real goods and services the nominal wage (W) will be able to command and is obviously influenced by the level of W and the price level. For a given W, the lower is P the greater the purchasing power of the nominal wage and so the higher is the real wage (w).

We write the real wage (w) as W/P. So if W = 10 and P = 1, then the real wage (w) = 10 meaning that the current wage will buy 10 units of real output. If P rose to 2 then w = 5, meaning the real wage was now cut by one-half.

Nominal GDP ($GDP) can be written as P.GDP, where the P values the real physical output.

Now if you put of these concepts together you get an interesting framework. To help you follow the logic here are the terms developed and be careful not to confuse $GDP (nominal) with GDP (real):

• Wage share = (W.L)/$GDP
• Nominal GDP: $GDP = P.GDP
• Labour productivity: LP = GDP/L
• Real wage: w = W/P

By substituting the expression for Nominal GDP into the wage share measure we get:

Wage share = (W.L)/P.GDP

In this area of economics, we often look for alternative way to write this expression – it maintains the equivalence (that is, obeys all the rules of algebra) but presents the expression (in this case the wage share) in a different “view”.

So we can write as an equivalent:

Wage share = (W/P).(L/GDP)

Now if you note that (L/GDP) is the inverse (reciprocal) of the labour productivity term (GDP/L). We can use another rule of algebra (reversing the invert and multiply rule) to rewrite this expression again in a more interpretable fashion.

So an equivalent but more convenient measure of the wage share is:

Wage share = (W/P)/(GDP/L) – that is, the real wage (W/P) divided by labour productivity (GDP/L).

I won’t show this but I could also express this in growth terms such that if the growth in the real wage equals labour productivity growth the wage share is constant. The algebra is simple but we have done enough of that already.

That journey might have seemed difficult to non-economists (or those not well-versed in algebra) but it produces a very easy to understand formula for the wage share.

Two other points to note. The wage share is also equivalent to the real unit labour cost (RULC) measures that Treasuries and central banks use to describe trends in costs within the economy. Please read my blog – Saturday Quiz – May 15, 2010 – answers and discussion – for more discussion on this point.

Now it becomes obvious that if the nominal wage (W) and the price level (P) are growing at the pace the real wage is constant. And if the real wage is growing at the same rate as labour productivity, then both terms in the wage share ratio are equal and so the wage share is constant.

However, if the real wage is falling we cannot conclude that the wage share is also falling. Given the nature of ratios, if the numerator (in this case, the real wage) is falling but not by as much as the denominator (in this case, labour productivity) then the overall ratio can actually be rising.

The following blogs may be of further interest to you:

• The origins of the economic crisis
• The fiscal stimulus worked but was captured by profits
• When will the workers wake up?

Question 3:

The automatic stabilisers operate to return the government budget balance returns to its appropriate level once growth returns following a downturn.

The answer is False.

The automatic stabilisers operate in a counter-cyclical fashion when economic growth resumes. This is because tax revenue improves given it is typically tied to income generation in some way. Further, most governments provide transfer payment relief to workers (unemployment benefits) and this increases when there is an economic slowdown.

The question is false though because this process while important may not ensure that the government budget balance returns to its appropriate level.

The automatic stabilisers just push the budget balance towards deficit, into deficit, or into a larger deficit when GDP growth declines and vice versa when GDP growth increases. These movements in aggregate demand play an important counter-cyclical attenuating role. So when GDP is declining due to falling aggregate demand, the automatic stabilisers work to add demand (falling taxes and rising welfare payments). When GDP growth is rising, the automatic stabilisers start to pull demand back as the economy adjusts (rising taxes and falling welfare payments).

We also measure the automatic stabiliser impact against some benchmark or “full capacity” or potential level of output, so that we can decompose the budget balance into that component which is due to specific discretionary fiscal policy choices made by the government and that which arises because the cycle takes the economy away from the potential level of output.

This decomposition provides (in modern terminology) the structural (discretionary) and cyclical budget balances. The budget components are adjusted to what they would be at the potential or full capacity level of output.

So if the economy is operating below capacity then tax revenue would be below its potential level and welfare spending would be above. In other words, the budget balance would be smaller at potential output relative to its current value if the economy was operating below full capacity. The adjustments would work in reverse should the economy be operating above full capacity.

If the budget is in deficit when computed at the “full employment” or potential output level, then we call this a structural deficit and it means that the overall impact of discretionary fiscal policy is expansionary irrespective of what the actual budget outcome is presently. If it is in surplus, then we have a structural surplus and it means that the overall impact of discretionary fiscal policy is contractionary irrespective of what the actual budget outcome is presently.

So you could have a downturn which drives the budget into a deficit but the underlying structural position could be contractionary (that is, a surplus). And vice versa.

The difference between the actual budget outcome and the structural component is then considered to be the cyclical budget outcome and it arises because the economy is deviating from its potential.

In some of the blogs listed below I go into the measurement issues involved in this decomposition in more detail. However for this question it these issues are less important to discuss.

The point is that structural budget balance has to be sufficient to ensure there is full employment. The only sensible reason for accepting the authority of a national government and ceding currency control to such an entity is that it can work for all of us to advance public purpose.

In this context, one of the most important elements of public purpose that the state has to maximise is employment. Once the private sector has made its spending (and saving decisions) based on its expectations of the future, the government has to render those private decisions consistent with the objective of full employment.

Given the non-government sector will typically desire to net save (accumulate financial assets in the currency of issue) over the course of a business cycle this means that there will be, on average, a spending gap over the course of the same cycle that can only be filled by the national government. There is no escaping that.

So then the national government has a choice – maintain full employment by ensuring there is no spending gap which means that the necessary deficit is defined by this political goal. It will be whatever is required to close the spending gap. However, it is also possible that the political goals may be to maintain some slack in the economy (persistent unemployment and underemployment) which means that the government deficit will be somewhat smaller and perhaps even, for a time, a budget surplus will be possible.

But the second option would introduce fiscal drag (deflationary forces) into the economy which will ultimately cause firms to reduce production and income and drive the budget outcome towards increasing deficits.

Ultimately, the spending gap is closed by the automatic stabilisers because falling national income ensures that that the leakages (saving, taxation and imports) equal the injections (investment, government spending and exports) so that the sectoral balances hold (being accounting constructs). But at that point, the economy will support lower employment levels and rising unemployment. The budget will also be in deficit – but in this situation, the deficits will be what I call “bad” deficits. Deficits driven by a declining economy and rising unemployment.

So fiscal sustainability requires that the government fills the spending gap with “good” deficits at levels of economic activity consistent with full employment – which I define as 2 per cent unemployment and zero underemployment.

Fiscal sustainability cannot be defined independently of full employment. Once the link between full employment and the conduct of fiscal policy is abandoned, we are effectively admitting that we do not want government to take responsibility of full employment (and the equity advantages that accompany that end).

So it will not always be the case that the dynamics of the automatic stabilisers will leave a structural deficit sufficient to finance the saving desire of the non-government sector at an output level consistent with full utilisation of resources.

The following blogs may be of further interest to you:

• A modern monetary theory lullaby
• Saturday Quiz – April 24, 2010 – answers and discussion
• The dreaded NAIRU is still about!
• Structural deficits – the great con job!
• Structural deficits and automatic stabilisers
• Another economics department to close

Question 4:

The government has to issue debt if the central bank is targetting a non-zero policy rate and is reluctant to pay a return on excess bank reserves.

The answer is True.

I am using the term government here in the Modern Monetary Theory (MMT) sense of the consolidation of the central bank and treasury operations.

Central banks conducts what are called liquidity management operations for two reasons. First, they have to ensure that all private cheques (that are funded) clear and other interbank transactions occur smoothly as part of its role of maintaining financial stability. Second, they must maintain aggregate bank reserves at a level that is consistent with their target policy setting given the relationship between the two.

So operating factors link the level of reserves to the monetary policy setting under certain circumstances. These circumstances require that the return on “excess” reserves held by the banks is below the monetary policy target rate. In addition to setting a lending rate (discount rate), the central bank also sets a support rate which is paid on commercial bank reserves held by the central bank.

Commercial banks maintain accounts with the central bank which permit reserves to be managed and also the clearing system to operate smoothly. In addition to setting a lending rate (discount rate), the central bank also can set a support rate which is paid on commercial bank reserves held by the central bank (which might be zero).

Many countries (such as Australia, Canada and zones such as the European Monetary Union) maintain a default return on surplus reserve accounts (for example, the Reserve Bank of Australia pays a default return equal to 25 basis points less than the overnight rate on surplus Exchange Settlement accounts). Other countries like Japan and the US have typically not offered a return on reserves until the onset of the current crisis.

If the support rate is zero then persistent excess liquidity in the cash system (excess reserves) will instigate dynamic forces which would drive the short-term interest rate to zero unless the government sells bonds (or raises taxes). This support rate becomes the interest-rate floor for the economy.

The short-run or operational target interest rate, which represents the current monetary policy stance, is set by the central bank between the discount and support rate. This effectively creates a corridor or a spread within which the short-term interest rates can fluctuate with liquidity variability. It is this spread that the central bank manages in its daily operations.

In most nations, commercial banks by law have to maintain positive reserve balances at the central bank, accumulated over some specified period. At the end of each day commercial banks have to appraise the status of their reserve accounts. Those that are in deficit can borrow the required funds from the central bank at the discount rate.

Alternatively banks with excess reserves are faced with earning the support rate which is below the current market rate of interest on overnight funds if they do nothing. Clearly it is profitable for banks with excess funds to lend to banks with deficits at market rates. Competition between banks with excess reserves for custom puts downward pressure on the short-term interest rate (overnight funds rate) and depending on the state of overall liquidity may drive the interbank rate down below the operational target interest rate. When the system is in surplus overall this competition would drive the rate down to the support rate.

The main instrument of this liquidity management is through open market operations, that is, buying and selling government debt. When the competitive pressures in the overnight funds market drives the interbank rate below the desired target rate, the central bank drains liquidity by selling government debt. This open market intervention therefore will result in a higher value for the overnight rate. Importantly, we characterise the debt-issuance as a monetary policy operation designed to provide interest-rate maintenance. This is in stark contrast to orthodox theory which asserts that debt-issuance is an aspect of fiscal policy and is required to finance deficit spending.

So the fundamental principles that arise in a fiat monetary system are as follows.

• The central bank sets the short-term interest rate based on its policy aspirations.
• Government spending is independent of borrowing which the latter best thought of as coming after spending.
• Government spending provides the net financial assets (bank reserves) which ultimately represent the funds used by the non-government agents to purchase the debt.
• Budget deficits put downward pressure on interest rates contrary to the myths that appear in macroeconomic textbooks about ‘crowding out’.
• The “penalty for not borrowing” is that the interest rate will fall to the bottom of the “corridor” prevailing in the country which may be zero if the central bank does not offer a return on reserves.
• Government debt-issuance is a “monetary policy” operation rather than being intrinsic to fiscal policy, although in a modern monetary paradigm the distinctions between monetary and fiscal policy as traditionally defined are moot.

Accordingly, debt is issued as an interest-maintenance strategy by the central bank. It has no correspondence with any need to fund government spending. Debt might also be issued if the government wants the private sector to have less purchasing power.

Further, the idea that governments would simply get the central bank to “monetise” treasury debt (which is seen orthodox economists as the alternative “financing” method for government spending) is highly misleading. Debt monetisation is usually referred to as a process whereby the central bank buys government bonds directly from the treasury.

In other words, the federal government borrows money from the central bank rather than the public. Debt monetisation is the process usually implied when a government is said to be printing money. Debt monetisation, all else equal, is said to increase the money supply and can lead to severe inflation.

However, as long as the central bank has a mandate to maintain a target short-term interest rate, the size of its purchases and sales of government debt are not discretionary. Once the central bank sets a short-term interest rate target, its portfolio of government securities changes only because of the transactions that are required to support the target interest rate.

The central bank’s lack of control over the quantity of reserves underscores the impossibility of debt monetisation. The central bank is unable to monetise the federal debt by purchasing government securities at will because to do so would cause the short-term target rate to fall to zero or to the support rate. If the central bank purchased securities directly from the treasury and the treasury then spent the money, its expenditures would be excess reserves in the banking system. The central bank would be forced to sell an equal amount of securities to support the target interest rate.

The central bank would act only as an intermediary. The central bank would be buying securities from the treasury and selling them to the public. No monetisation would occur.

However, the central bank may agree to pay the short-term interest rate to banks who hold excess overnight reserves. This would eliminate the need by the commercial banks to access the interbank market to get rid of any excess reserves and would allow the central bank to maintain its target interest rate without issuing debt.

The following blogs may be of further interest to you:

• Saturday Quiz – May 1, 2010 – answers and discussion
• Understanding central bank operations
• Building bank reserves will not expand credit
• Building bank reserves is not inflationary
• Deficit spending 101 – Part 1
• Deficit spending 101 – Part 2
• Deficit spending 101 – Part 3

Premium Question 5:

Assume that inflation and nominal interest rates are both constant and zero and a country has a public debt to GDP ratio of 100 per cent. The approach taken by those who support fiscal austerity is to run primary budget surpluses to stabilise and then reduce the debt ratio. Under the circumstances given, this strategy can still work if the economy contracts under the burden of the surpluses.

The answer is True.

First, some background theory and conceptual development.

While Modern Monetary Theory (MMT) places no particular importance in the public debt to GDP ratio for a sovereign government, given that insolvency is not an issue, the mainstream debate is dominated by the concept. The unnecessary practice of fiat currency-issuing governments of issuing public debt $-for-$ to match public net spending (deficits) ensures that the debt levels will always rise when there are deficits.

But the rising debt levels do not necessarily have to rise at the same rate as GDP grows. The question is about the debt ratio not the level of debt per se.

Rising deficits often are associated with declining economic activity (especially if there is no evidence of accelerating inflation) which suggests that the debt/GDP ratio may be rising because the denominator is also likely to be falling or rising below trend.

Further, historical experience tells us that when economic growth resumes after a major recession, during which the public debt ratio can rise sharply, the latter always declines again.

It is this endogenous nature of the ratio that suggests it is far more important to focus on the underlying economic problems which the public debt ratio just mirrors.

Mainstream economics starts with the flawed analogy between the household and the sovereign government such that any excess in government spending over taxation receipts has to be “financed” in two ways: (a) by borrowing from the public; and/or (b) by “printing money”.

Neither characterisation is remotely representative of what happens in the real world in terms of the operations that define transactions between the government and non-government sector.

Further, the basic analogy is flawed at its most elemental level. The household must work out the financing before it can spend. The household cannot spend first. The government can spend first and ultimately does not have to worry about financing such expenditure.

However, the mainstream framework for analysing these so-called “financing” choices is called the government budget constraint (GBC). The GBC says that the budget deficit in year t is equal to the change in government debt over year t plus the change in high powered money over year t. So in mathematical terms it is written as:

which you can read in English as saying that Budget deficit = Government spending + Government interest payments – Tax receipts must equal (be “financed” by) a change in Bonds (B) and/or a change in high powered money (H). The triangle sign (delta) is just shorthand for the change in a variable.

However, this is merely an accounting statement. In a stock-flow consistent macroeconomics, this statement will always hold. That is, it has to be true if all the transactions between the government and non-government sector have been correctly added and subtracted.

So in terms of MMT, the previous equation is just an ex post accounting identity that has to be true by definition and has no real economic importance.

But for the mainstream economist, the equation represents an ex ante (before the fact) financial constraint that the government is bound by. The difference between these two conceptions is very significant and the second (mainstream) interpretation cannot be correct if governments issue fiat currency (unless they place voluntary constraints on themselves and act as if it is a financial constraint).

Further, in mainstream economics, money creation is erroneously depicted as the government asking the central bank to buy treasury bonds which the central bank in return then prints money. The government then spends this money.

This is called debt monetisation and you can find out why this is typically not a viable option for a central bank by reading the Deficits 101 suite – Deficit spending 101 – Part 1 – Deficit spending 101 – Part 2 – Deficit spending 101 – Part 3.

Anyway, the mainstream claims that if governments increase the money growth rate (they erroneously call this “printing money”) the extra spending will cause accelerating inflation because there will be “too much money chasing too few goods”! Of-course, we know that proposition to be generally preposterous because economies that are constrained by deficient demand (defined as demand below the full employment level) respond to nominal demand increases by expanding real output rather than prices. There is an extensive literature pointing to this result.

So when governments are expanding deficits to offset a collapse in private spending, there is plenty of spare capacity available to ensure output rather than inflation increases.

But not to be daunted by the “facts”, the mainstream claim that because inflation is inevitable if “printing money” occurs, it is unwise to use this option to “finance” net public spending.

Hence they say as a better (but still poor) solution, governments should use debt issuance to “finance” their deficits. Thy also claim this is a poor option because in the short-term it is alleged to increase interest rates and in the longer-term is results in higher future tax rates because the debt has to be “paid back”.

Neither proposition bears scrutiny – you can read these blogs – Will we really pay higher taxes? and Will we really pay higher interest rates? – for further discussion on these points.

The mainstream textbooks are full of elaborate models of debt pay-back, debt stabilisation etc which all claim (falsely) to “prove” that the legacy of past deficits is higher debt and to stabilise the debt, the government must eliminate the deficit which means it must then run a primary surplus equal to interest payments on the existing debt.

A primary budget balance is the difference between government spending (excluding interest rate servicing) and taxation revenue.

The standard mainstream framework, which even the so-called progressives (deficit-doves) use, focuses on the ratio of debt to GDP rather than the level of debt per se. The following equation captures the approach:

So the change in the debt ratio is the sum of two terms on the right-hand side: (a) the difference between the real interest rate (r) and the GDP growth rate (g) times the initial debt ratio; and (b) the ratio of the primary deficit (G-T) to GDP.

The real interest rate is the difference between the nominal interest rate and the inflation rate.

Many mainstream economists and a fair number of so-called progressive economists say that governments should as some point in the business cycle run primary surpluses (taxation revenue in excess of non-interest government spending) to start reducing the debt ratio back to “safe” territory.

Almost all the media commentators that you read on this topic take it for granted that the only way to reduce the public debt ratio is to run primary surpluses. That is what the whole “credible exit strategy” rhetoric is about and what is driving the austerity push around the world at present.

The standard formula above can easily demonstrate that a nation running a primary deficit can reduce its public debt ratio over time. So it is clear that the public debt ratio can fall even if there is an on-going budget deficit if the real GDP growth rate is strong enough. This is win-win way to reduce the public debt ratio.

But the question is analysing the situation where the government is desiring to run primary budget surpluses.

Consider the following Table which captures the variations possible in the question. In Year 1, the B/Y(-1) = 1 (that is, the public debt ratio at the start of the period is 100 per cent). The (-1) just signals the value inherited in the current period. We have already assumed that the inflation rate and the nominal interest rate are constant and zero, which means that the real interest rate is also zero and constant. So the r term in the model is 0 throughout our stylised simulation.

This is not to dissimilar to the situation at present in many countries.

In Year 1, there is zero real GDP growth and the Primary Budget Balance is also zero. Under these circumstances, the debt ratio is stable.

Now in Year 2, the fiscal austerity program begins and assume for the sake of discussion that it doesn’t dent real GDP growth. In reality, a major fiscal contraction is likely to push real GDP growth into the negative (that is, promote a recession). But for the sake of the logic we assume that nominal GDP growth is 1 per cent in Year 2, which means that real GDP growth is also 1 per cent given that all the nominal growth is real (zero inflation).

We assume that the government succeeds in pushing the Primary Budget Surplus to 1 per cent of GDP. This is the mainstream nirvana – the public debt ratio falls by 2 per cent as a consequence.

In Year 3, we see that the Primary Budget Surplus remains positive (0.5 per cent of GDP) but is now below the positive real GDP growth rate. In this case the public debt ratio still falls.

In Year 4, real GDP growth contracts (0.5 per cent) and the Primary Budget Surplus remains positive (1 per cent of GDP). In this case the public debt ratio still false which makes the proposition in the question false.

So if you have zero real interest rates, then even in a recession, the public debt ratio can still fall and the government run a budget surplus as long as Primary Surplus is greater in absolute value to the negative real GDP growth rate. Of-course, this logic is just arithmetic based on the relationship between the flows and stocks involved. In reality, it would be hard for the government to run a primary surplus under these conditions given the automatic stabilisers would be undermining that aim.

In Year 5, the real GDP growth rate is negative 1.5 per cent and the Primary Budget Surplus remains positive at 1 per cent of GDP. In this case the public debt ratio rises.

The best way to reduce the public debt ratio is to stop issuing debt. A sovereign government doesn’t have to issue debt if the central bank is happy to keep its target interest rate at zero or pay interest on excess reserves.

The discussion also demonstrates why tightening monetary policy makes it harder for the government to reduce the public debt ratio – which, of-course, is one of the more subtle mainstream ways to force the government to run surpluses.

The following blog may be of further interest to you:

• Saturday Quiz – November 27, 2010 – answers and discussion