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Posts Tagged ‘irrational behaviour’

Irrational exuberance

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?
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How behavioural economics can help you stick to New Year’s resolutions

Many or us make New Year’s resolutions: going on a diet, doing exercise, spending more time studying. But few people stick to them, even though they say they would like to. So how can people be motivated to keep to their resolutions? Well, the experiments of behavioural economists provide a number of insights into the problem. They also suggest various incentives that can be used to motivate people to stick to their plans.

Central to the problem is that people have ‘time inconsistency’. They put a higher weight on the benefits of things that are good for them in the future and less weight on these benefits when they have to act now. You might strongly believe that going to the gym is good for you and plan to go next Monday. But when Monday comes, you can’t face it.

Another part of the time inconsistency problem is the relatively high weighting given to short-term gratification – eating chocolates, watching TV, spending time on social media, staying in bed. When thinking about whether you would like to do these things in, say, a couple of days’ time, you put a low weight on the pleasures. But thinking about doing them right now, you put a much higher weight on them. As the well-known saying goes, ‘Hard work often pays off after time, but laziness pays off now’.

So how can people be motivated to stick to their resolutions? Behavioural economists have studied various systems of incentives to see what works. Some of the findings are as follows:

•  People are generally loss averse. To get us to stick to New Year’s resolutions, we could devise a system of penalties for breaking them, such as paying 20p each time you swear!
•  Given people’s time inconsistency, devising a system whereby you get treats after doing something you feel is good for you: e.g. watching TV for 30 minutes after you’ve done an hour’s revision. Rewards should follow effort, not precede them.
•  Having simple clear goals. Thus rather than merely saying ‘I’ll eat less’, you devise a meal plan with menus that meet calorie and other dietary goals. Rather than saying, ‘I’ll exercise more’, you commit to going to the gym at specific times each week and doing a specific amount of each exercise.
•  Ritualising. This is where you devise a regime that is feasible to stick to. For example, you could always write a shopping list to meet your dietary goals and then only buy what’s on that list; or you and your flatmates could have a rota for household chores.
•  Social reinforcement. This is where people have a joint plan and help each other stick to it, such as going to the gym at specific times with a friend or group of friends, or joining a support group (e.g. to lose weight, or give up drinking or smoking).
•  Avoiding temptation. For example, if you want to give up chocolate, don’t have any in the house.
•  Using praise rather than criticism. People generally respond better to positive incentives than negative ones.

Behavioural economists test these different incentive mechanisms to see what works best and then to see how they can be refined. The testing could be done experimentally, with volunteers being given different incentives and seeing how they respond. Alternatively, data could be collected on the effects of different incentive mechanisms that people have actually used, whether at home or at work.

The advertising and marketing industry analyses consumer trends and how people respond to pricing, quality, display, packaging, advertising, etc. They want to understand human behaviour so that they can ‘direct’ it in their favour of their clients. Governments too are keen to find ways of encouraging people to do more of things that are good for them and less of things that are bad.

The UK government’s Behavioural Insights Team looks at ways people can be ‘nudged’ into changing their behaviour, see the blog A nudge in the right direction?

But back to New Year’s resolutions, have you made any? And, if so, have you thought about how you might stick to them? Have you thought about the incentives?

Dan Ariely talks “Payoff” WUNC 91.5: North Carolina Public Radio, Dan Ariely talks to Frank Stasio (3/1/17)

Articles and blogs
50 New Year’s Resolution Ideas and how to Achieve Each of Them Lifehack, Ivan Dimitrijevic (31/12/16)
5 New Year’s Resolutions You Can Keep (With The Help Of Behavioral Science Research) Forbes, Carmen Nobel (3/1/17)
The science behind keeping your New Year’s resolutions BT, SNAP PA (30/12/15)
The Guardian view on New Year resolutions: fitter, happier, more productive The Guardian, Editorial (3/1/17)
The Behavioral Economics of Your New Year’s Resolutions The Daily Beast, Uri Gneezy (5/1/14)
The psychology of New Year’s resolution The Conversation, Mark Griffiths (1/1/16)
Apply Behavioral Economics for a Better New Year Wharton Blog Network, William Hartje (16/1/14)
The Kardashians Can Help Your New Year’s Resolutions Huffington Post, John Beeby (29/12/16)
Using economics to score with New Year resolutions The Hindu, Venky Vembu (4/1/17)
Be It Resolved The New York Times, John Tierney (5/1/12)

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  1. Explain what is meant by time inconsistent behaviour. Is this the same as giving future costs and benefits a lower weighting than present ones (and hence having to discount future costs and benefits)?
  2. Give some examples of ways in which your own behaviour exhibits time inconsistency. Would it be accurate to describe this as ‘present bias’?
  3. Would you describe not sticking to New Year’s resolutions as ‘irrational behaviour’?
  4. Have you made any New Year’s resolutions, or do you have any plans to achieve goals? Could you alter your own personal incentives and, if so, how, to make it more likely that you will stick to your resolutions/goals?
  5. Give some examples of ways in which the government could ‘nudge’ us to behave in ways that were more in our own individual interests or those of society or the environment?
  6. Do you think it’s desirable that the advertising industry should employ psychologists and behavioural economists to help it achieve its goals?
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