Tag: accelerator

Both the financial and goods markets are heavily influenced by sentiment. And such sentiment tends to be self-reinforcing. If consumers and investors are pessimistic, they will not spend and not invest. The economy declines and this further worsens sentiment and further discourages consumption and investment. Banks become less willing to lend and stock markets fall. The falling stock markets discourage people from buying shares and so share prices fall further. The despondency becomes irrational and greatly exaggerates economic fundamentals.

This same irrationality applies in a boom. Here it becomes irrational exuberance. A boom encourages confidence and stimulates consumer spending and investment. This further stimulates the boom via the multiplier and accelerator and further inspires confidence. Banks are more willing to lend, which further feeds the expansion. Stock markets soar and destabilising speculation further pushes up share prices. There is a stock market bubble.

But bubbles burst. The question is whether the current global stock market boom, with share prices reaching record levels, represents a bubble. One indicator is the price/earnings (PE) ratio of shares. This is the ratio of share prices to earnings per share. Currently the ratio for the US index, S&P 500, is just over 26. This compares with a mean over the past 147 years of 15.64. The current ratio is the third highest after the peaks of the early 2000s and 2008/9.

An alternative measure of the PE ratio is the Shiller PE ratio (see also). This is named after Robert Shiller, who wrote the book Irrational Exuberance. Unlike conventional PE ratios, which only look at average earnings over the past four quarters, the Shiller PE ratio uses average earnings over the past 10 years. “Because this factors in earnings from the previous ten years, it is less prone to wild swings in any one year.”

The current level of the Shiller PE ratio is 29.14, the third highest on record, this time after the period running up to the Wall Street crash of 1929 and the dot-com bubble of the late 1990s. The mean Shiller PE ratio over the past 147 years is 16.72.

So are we in a period of irrational exuberance? And are stock markets experiencing a bubble that sooner or later will burst? The following articles explore these questions.


2 Clear Instances of Irrational Exuberance Seeking Alpha, Jeffrey Himelson (12/2/17)
Promised land of Trumpflation-inspired global stimulus has been slow off the mark South China Morning Post, David Brown (20/2/17)
A stock market crash is a way off, but this boom will turn to bust The Guardian, Larry Elliott (16/2/17)
The “boring” bubble is close to bursting – the Unilever bid proves it MoneyWeek, John Stepek (20/2/17)


  1. Find out what is meant by Minksy’s ‘financial instability hypothesis’ and a ‘Minsky moment’. How might they explain irrational exuberance and the sudden turning point from a boom to a bust?
  2. Is it really irrational to buy shares with a very high PE ratio if everyone else is doing so?
  3. Why are people currently exuberant?
  4. What might cause the current exuberance to end?
  5. How does irrational exuberance affect the size of the multiplier?
  6. How might the behaviour of banks and other financial institutions contribute towards a boom fuelled by irrational exuberance?
  7. Compare the usefulness of a standard PE ratio with the Shiller PE ratio.
  8. Other than high PE ratios, what else might suggest that stock markets are overvalued?
  9. Why might a company’s PE ratio differ from its price/dividends ratio (see)? Which is a better measure of whether or not a share is overvalued?

Many politicians throughout the world,
not just on the centre and left, are arguing for increased spending on infrastructure. This was one of the key proposals of Donald Trump during his election campaign. In his election manifesto he pledged to “Transform America’s crumbling infrastructure into a golden opportunity for accelerated economic growth and more rapid productivity gains”.

Increased spending on inffrastructure has both demand- and supply-side effects.

Unless matched by cuts elsewhere, such spending will increase aggregate demand and could have a high multiplier effect if most of the inputs are domestic. Also there could be accelerator effects as the projects may stimulate private investment.

On the supply side, well-targeted infrastructure spending can directly increase productivity and cut costs of logistics and communications.

The combination of the demand- and supply-side effects could increase both potential and actual output and reduce unemployment.

So, if infrastructure projects can have such beneficial effects, why are politicians often so reluctant to give them the go-ahead?

Part of the problem is one of timing. The costs occur in the short run. These include demolition, construction and disruption. The direct benefits occur in the longer term, once the project is complete. And for complex projects this may be many years hence. It is true that demand-side benefits start to occur once construction has begun, but these benefits are widely dispersed and not easy to identify directly with the project.

Then there is the problem of externalities. The external costs of projects may include environmental costs and costs to local residents. This can lead to protests, public hearings and the need for detailed cost–benefit analysis. This can delay or even prevent projects from occurring.

The external benefits are to non-users of the project, such as a new bridge or bypass reducing congestion for users of existing routes. These make the private construction of many projects unprofitable, except with public subsidies or with public–private partnerships. So there does need to be a macroeconomic policy that favours publicly-funded infrastructure projects.

One type of investment that is less disruptive and can have shorter-term benefits is maintenance investment. Maintenance expenditure can avoid much more costly rebuilding expenditure later on. But this is often the first type of expenditure to be cut when public-sector budgets as squeezed, whether at the local or national level.

The problem of lack of infrastructure investment is very much a political problem. The politicians who give the go-ahead to such projects, such as high-speed rail, come in for criticisms from those bearing the short-run costs but they are gone from office once the benefits start to occur. They get the criticism but not the praise.


Are big infrastructure projects castles in the air or bridges to nowhere? The Economist, Buttonwood’s notebook (16/1/17)
Trump’s plans to rebuild America are misguided and harmful. This is how we should do it. The Washington Post, Lawrence H. Summers (17/1/17)


  1. Identify the types of externality from (a) a new high-speed rail line, (b) new hospitals.
  2. How is discounting relevant to decisions about public-sector projects?
  3. Why are governments often unwilling to undertake (a) new infrastructure projects, (b) maintenance projects?
  4. Is a programme of infrastructure investment necessarily a Keynesian policy?
  5. What accelerator effects would you expect from infrastructure investment?
  6. Explain the difference between the ‘spill-out’ and ‘pull-in’ effects of different types of public investments in a specific location. Is it possible for a project to have both effects?
  7. What answer would you give to the teacher who asked the following question of US Treasury Secretary, Larry Summers? “The paint is chipping off the walls of this school, not off the walls at McDonald’s or the movie theatre. So why should the kids believe this society thinks their education is the most important thing?”
  8. What is the ‘bridge to nowhere’ problem? Why does it occur and what are the solutions to it?
  9. Why is the ‘castles in the air’ element of private projects during a boom an example of the fallacy of composition?

As we saw in Part 1 of this blog, oil prices have fallen by some 46% in the past five months. In that blog we looked at the implications for fuel prices. Here we look at the broader implications for the global economy? Is it good or bad news – or both?

First we’ll look at the oil-importing countries. To some extent the lower oil price is a reflection of weak global demand as many countries still struggle to recover from recession. If the lower price boosts demand, this may then cause the oil price to rise again. At first sight, this might seem merely to return the world economy to the position before the oil price started falling: a leftward shift in the demand for oil curve, followed by a rightward shift back to where it was. However, the boost to demand in the short term may act as a ‘pump primer’. The higher aggregate demand may result in a multiplier effect and cause a sustained increase in output, especially if it stimulates a rise in investment through rising confidence and the accelerator, and thereby increases capacity and hence potential GDP.

But the fall in the oil price is only partly the result of weak demand. It is mainly the result of increased supply as new sources of oil come on stream, and especially shale oil from the USA. Given that OPEC has stated that it will not cut its production, even if the crude price falls to $40 per barrel, the effect has been a shift in the oil supply curve to the right that will remain for some time.

So even if the leftward shift in demand is soon reversed so that there is then some rise in oil prices again, it is unlikely that prices will rise back to where they were. Perhaps, as the diagram illustrates, the price will rise to around $70 per barrel. It could be higher if world demand grows very rapidly, or if some sources of supply go off stream because at such prices they are unprofitable.

The effect on oil exporting countries has been negative. The most extreme case is Russia, where for each $10 fall in the price of oil, its growth rate falls by around 1.4 percentage points (see). Although the overall effect on global growth is still likely to be positive, the lower oil price could lead to a significant cut in investment in new oil wells. North sea producers are predicting a substantial cut in investment. Even shale oil producers in the USA, where the marginal cost of extracting oil from existing sources is only around $10 to £20 per barrel, need a price of around $70 or more to make investment in new sources profitable. What is more, typical shale wells have a life of only two or three years and so lack of investment would relatively quickly lead to shale oil production drying up.

The implication of this is that although there has been a rightward shift in the short-run supply curve, if price remains low the curve could shift back again, meaning that the long-run supply curve is much more elastic. This could push prices back up towards $100 if global demand continues to expand.

This can be illustrated in the diagram. The starting point is mid-2014. Global demand and supply are D1 and S1; price is $112 per barrel and output is Q1. Demand now shifts to the left and supply to the right to D2 and S2 respectively. Price falls to $60 per barrel and, given the bigger shift in supply than demand, output rises to Q2. At $60 per barrel, however, output of Q2 cannot be sustained. Thus at $60, long-run supply (shown by SL) is only Q4.

But assuming the global economy grows over the coming months, demand shifts to the right: say, to D3. Assume that it pushes price up to $100 per barrel. This gives a short-run output of Q3, but at that price it is likely that supply will be sustainable in the long run as it makes investment sufficiently profitable. Thus curve D3 intersects with both S2 and SL at this price and quantity.

The articles below look at the gainers and losers and at the longer-term effects.


Where will the oil price settle? BBC News, Robert Peston (22/12/14)
Falling oil prices: Who are the winners and losers? BBC News, Tim Bowler (16/12/14)
Why the oil price is falling The Economist (8/12/14)
The new economics of oil: Sheikhs v shale The Economist (6/12/14)
Shale oil: In a bind The Economist (6/12/14)
Falling Oil Price slows US Fracking Oil-price.net, Steve Austin (8/12/14)
Oil Price Drop Highlights Need for Diversity in Gulf Economies IMF Survey (23/12/14)
Lower oil prices boosting global economy: IMF Argus Media (23/12/14)
Collapse in oil prices: producers howl, consumers cheer, economists fret The Guardian (16/12/14)
North Sea oilfields ‘near collapse’ after price nosedive The Telegraph, Andrew Critchlow (18/12/14)
How oil price fall will affect crude exporters – and the rest of us The Observer, Phillip Inman (21/12/14)
Cheaper oil could damage renewable energies, says Richard Branson The Guardian,
Richard Branson: ‘Governments are going to have to think hard how to adapt to low oil prices.’ John Vidal (16/12/14)


Brent crude prices U.S. Energy Information Administration (select daily, weekly, monthly or annual data and then download to Excel)
Brent Oil Historical Data Investing.com (select daily, weekly, or monthly data and time period)


  1. What would determine the size of the global multiplier effect from the cut in oil prices?
  2. Where is the oil price likely to settle in (a) six months’ time; (b) two years’ time? What factors are you taking into account in deciding your answer?
  3. Why, if the average cost of producing oil from a given well is $70, might it still be worth pumping oil and selling it at a price of $30?
  4. How does speculation affect oil prices?
  5. Why has OPEC decided not to cut oil production even though this is likely to drive the price lower?
  6. With Brent crude at around $60 per barrel, what should North Sea oil producers do?
  7. If falling oil prices lead some oil-importing countries into deflation, what will be the likely macroeconomic impacts?

The Preliminary Estimate of the UK Q2 GDP figures by the Office for National Statistics show that the UK economy grew by 0.6% in the second quarter of 2013: double the growth rate of the first quarter and almost back to the long-run average growth rate prior to 2008.

At first sight, this would seem to be good news – certainly from the government’s point of view. What is more, unlike the previous quarter, growth is spread relatively evenly across the three main sectors: the production (manufacturing, mining, water supply, etc.) and services sectors both grew by 0.6% and the construction sector by 0.9% (this sector fell by 1.8% in the previous quarter). (Click here for a PowerPoint of the chart below.)

But while growth in the latest quarter may be balanced between the broad sectors, the rise in aggregate demand is not balanced between its components. As an earlier news item (A balancing act) showed, the rise in aggregate demand has been driven largely by a rise in consumption, and a corresponding fall in saving. Exports are rising only slowly and investment is some 25% lower than in the boom years prior to 2008.

So will the latest growth be sustainable? Will investment now begin to pick up and what constraints are there on investment? The following articles consider some of the issues.


Economy firing on all cylinders as growth hits 0.6pc The Telegraph, Philip Aldrick (25/7/13)
The good, the bad or the ugly? How the UK economy stands up. The Telegraph, Philip Aldrick (25/7/13)
George Osborne’s 0.6% growth is good but unspectacular The Guardian, Larry Elliott (25/7/13)
The (not-so) green shoots of recovery The Economist, John Van Reenen (23/7/13)
Economic recovery slow to take root for some in UK Reuters, William Schomberg and Max De Haldevang (25/7/13)
GDP figures offer hard evidence for political narrative BBC News, Paul Mason (25/7/13)
Ignore the hype: Britain’s ‘recovery’ is a fantasy that hides our weakness The Observer, Will Hutton (21/7/13)
UK economy: Half-speed ahead BBC News, Stephanie Flanders (25/7/13)
BoE guidance can help sustain the UK recovery The Economist, Kevin Daly (22/7/13)
George Osborne’s description of the economy is near-Orwellian The Guardian, Ha-Joon Chang (26/7/13)
Economic growth: more must be done to encourage investment The Guardian, Phillip Inman (1/8/13)


Gross Domestic Product: Preliminary Estimate, Q2 2013 ONS (25/7/13)


  1. Compare the macroeconomic situation today with that prior to the financial crisis of 2007/8 and subsequent recession.
  2. What factors will determine the sustainability of the UK economic recovery?
  3. What is meant by the ‘accelerator’ and what will determine the size of any accelerator effect from the latest rise in UK GDP?
  4. What supply-side constraints are likely to limit the rate and extent of recovery?
  5. Why do economies that are in recession ‘naturally bounce back’ without any government intervention? Have the macroeconomic policies of the UK government helped or hindered this bounce back? Explain.
  6. What monetary measures by the Bank of England are most appropriate in the current circumstances?

There’s some good news and some bad news about the UK economy. The good news is that there are signs that the recovery is gathering momentum; the ‘green shoots’ are growing bigger. The bad news is that it’s the ‘wrong type of growth’!

One of the main underlying problems of the 2008 financial crisis was that household debt had been increasing to unsustainable levels, egged on by banks only too willing to lend, whether as personal loans, on credit cards or through mortgages. When the recession hit, many people sought to reduce their debts by cutting back on spending. This further fuelled the recession.

What the government and most economists hoped was that there would be some rebalancing of the economy, with less reliance on consumer spending to drive economic growth. Instead it was hoped that growth would be driven by a rise in investment and exports. Indeed, the 25% depreciation of sterling exchange between 2007 and 2009 was seen as a major advantage as this would boost the demand for exports and encourage firms to invest in the export sector.

But things haven’t turned out the way people hoped. The recession (or lack of growth) has been much deeper and more prolonged than previous downturns in the economy. Today, real GDP per head is more than 7% below the level in 2007 and many people have seen much bigger declines in their living standards.

But also, despite the austerity policies, the economy has not been ‘rebalanced’ towards exports and investment. Exports are 3% lower than in 2006 (although they did grow between 2009 Q2 and 2011 Q1, but have since stagnated). And investment is 27% lower than in 2006. Household consumption, however, has grown by about 2% and general government consumption by around 9% since 2006. The chart shows the figures, based on 2006 Q1 = 100.
(Click here for a PowerPoint of the chart.)

And recent evidence is that consumption is beginning to grow faster – not because of rising household incomes, but because of falling saving rates. In 2008, the household saving ratio had fallen to nearly 0% (i.e. households were on average saving about the same as they were borrowing). Then the saving ratio rose dramatically as people reined in their spending. Between 2009 and 2012, the ratio hovered around 7%. But in the first quarter of 2013, it had fallen to 4.2%

So the good news is that aggregate demand is rising, boosting economic growth. But the bad news is that, at least for the time being, this growth is being driven by a rise in household borrowing and a fall in household saving. The videos and articles consider whether this is, however, still good news on balance.


Britain’s imbalanced economy The Economist, Zanny Minton Beddoes and Richard Davies (4/7/13)
Britain’s Export Drought: an enduring disappointment The Economist, Andrew Palmer and Richard Davies (9/2/13)
‘Green shoots’ of economic recovery in Rugby BBC News, Paul Mason (12/6/13)


Is the UK economy seeing the ‘wrong kind’ of green shoots? BBC News, Stephanie Flanders (3/7/13)
The export drought: Better out than in The Economist (9/2/13)
Exports and the economy: Made in Britain The Economist (21/1/12)
The economy: On a wing and a credit card The Economist (6/7/13)
Unbalanced and unsustainable – this is the wrong kind of growth The Telegraph, Jeremy Warner (8/7/13)
The UK economy’s looking up – but no one’s told manufacturers The Guardian, Heather Stewart (10/7/13)


Quarterly National Accounts, Q1 2013 (27/6/13)
Forecasts for the UK economy: a comparison of independent forecasts HM Treasury (June 2013)
ISM Manufacturing Report on Business® PMI History Institute for Supply Management


  1. What are forecasters expecting to happen to economic growth in the coming months? Why?
  2. What factors determine investment? Why has it fallen so substantially in the UK?
  3. Explain what is meant by the ‘accelerator’. Is the rise in consumption likely to lead to an accelerator effect and, if so, what will determine the size of this effect?
  4. Why have exports not grown more rapidly despite the depreciation of sterling after 2007?
  5. What will determine the rate of potential economic growth in the UK economy? How will a rise in real GDP driven by a rise in consumption impact on potential GDP and potential economic growth?
  6. What supply-side policies would you recommend, and why, in order to increase potential economic growth?