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Posts Tagged ‘social rate of discount’

Hurricanes and the social rate of discount

With first Houston, then several Caribbean islands and Florida suffering dreadful flooding and destruction from Hurricanes Harvey and Irma, many are questioning whether more should be spent on flood prevention and reducing greenhouse gas emissions. Economists would normally argue that such questions are answered by conducting a cost–benefit analysis.

However, even if the size of the costs and benefits of such policies could be measured, this would not be enough to give the answer. Whether such spending is justified would depend on the social rate of discount. But what the rate should be in cost-benefit analyses is a highly contested issue, especially when the benefits occur a long time in the future.

I you ask the question today, ‘should more have been spent on flood prevention in Houston and Miami?’, the answer would almost certainly be yes, even if the decision had to have been taken many years ago, given the time it takes to plan and construct such defences. But if you asked people, say, 15 years ago whether such expenditure should be undertaken, many would have said no, given that the protection would be provided quite a long time in the future. Also many people back then would doubt that the defences would be necessary and many would not be planning to live there indefinitely.

This is the familiar problem of people valuing costs and benefits in the future less than costs and benefits occurring today. To account for this, costs and benefits in the future are discounted by an annual rate to reduce them to a present value.

But with costs and benefits occurring a long time in the future, especially from measures to reduce carbon emissions, the present value is very sensitive to the rate of discount chosen. But choosing the rate of discount is fraught with difficulties.

Some argue that a social rate of discount should be similar to long-term market rates. But market rates reflect only the current generation’s private preferences. They do not reflect the costs and benefits to future generations. A social rate of discount that did take their interests into account would be much lower and could even be argued to be zero – or negative with a growing population.

Against this, however, has to be set the possibility that future generations will be richer than the current one and will therefore value a dollar (or any other currency) less than today’s generation.

However, it is also likely, if the trend of recent decades is to continue, that economic growth will be largely confined to the rich and that the poor will be little better off, if at all. And it is the poor who often suffer the most from natural disasters. Just look, for example, at the much higher personal devastation suffered from hurricane Irma by the poor on many Caribbean islands compared with those in comparatively wealthy Florida.

A low or zero discount rate would make many environmental projects socially profitable, even though they would not be with a higher rate. The choice of rate is thus crucial to the welfare of future generations who are likely to bear the brunt of climate change.

But just how should the social rate of discount be chosen? The following two articles explore the issue.

How Much Is the Future Worth? Slate, Will Oremus (1/9/17)
Climate changes the debate: The impact of demographics on long-term discount rates Vox, Eli P Fenichel, Matthew Kotchen and Ethan T Addicott (20/8/17)


  1. What is meant by the social rate of discount?
  2. Why does the choice of a lower rate of social discount imply a more aggressive climate policy?
  3. How is the distribution of the benefits and costs of measures to reduce carbon emissions between rich and poor relevant in choosing the social rate of discount of such measures?
  4. How is the distribution of the benefits of such measures between current and future generations relevant in choosing the rate?
  5. How is uncertainty about the magnitude of the costs and benefits relevant in choosing the rate?
  6. What is the difference between Stern’s and Nordhaus’ analyses of the choice of social discount rate?
  7. Explain and discuss the ‘mortality-based approach’ to estimating social discount rates.
  8. What are the arguments ‘for economists analysing climate change through the lens of minimising risk, rather than maximizing utility’?
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Going nuclear

The UK government has just given the go-ahead for the building of two new nuclear reactors at Hinkley Point in Somerset. The contract to build and run the power station will go to EDF, the French energy company.

The power station is estimated to cost some £14 billion to build. It would produce around 7% of the UK’s electricity. Currently the 16 nuclear reactors in the UK produce around 19%. But all except for Sizewell B in Suffolk are due to close by 2023, although the lives of some could be extended. There is thus a considerable energy gap to fill in the coming years.

Several new nuclear power stations were being considered to help fill this gap, but with rising capital costs, especially following the Fukushima disaster in Japan, potential investors pulled out of other negotiations. Hinkley Point is the only proposal left. It’s not surprising that the government wants it to go ahead.

All that remains to agree is the price that EDF can charge for the electricity generated from the power station. This price, known as the ‘strike price’, is a government-guaranteed price over the long term. EDF is seeking a 40-year deal. Some low carbon power stations, such as nuclear and offshore wind and wave power stations, have high capital costs. The idea of the strike price is to reduce the risks of the investment and make it easier for energy companies to estimate the likely return on capital.

But the strike price, which will probably be agreed at around £95 per megawatt hour (MWh), is roughly double the current wholesale price of electricity. EDF want a price of around £100 per MWh, which is estimated to give a return on capital of around 10%. The government was hoping to agree on a price nearer to £80 per MWh. Either way, this will require a huge future subsidy on the electricity generated from the plant.

There are several questions being asked about the deal. Is the strike price worth paying? Are all the costs and benefits properly accounted for, including environmental costs and benefits and safety issues? Being an extremely long-term project, are uncertainties over costs, performance of the plant, future market prices for electricity and the costs of alternative forms of power generation sufficiently accounted for? Will the strike price contravene EU competition law? Is the timescale for construction realistic and what would be the consequences of delays? The articles consider these questions and raise a number of issues in planning very long-term capital projects.

Hinkley Point: Britain’s second nuclear age given green light as planning permission is approved for first of new generation atomic power stations Independent, Michael McCarthy (19/3/13)
Will they or won’t they? New nuclear hangs in the balance ITV News, Laura Kuenssberg (19/3/13)
Hinkley Point C: deal or no deal for UK nuclear? The Telegraph, Alistair Osborne (19/3/13)
New nuclear power plant at Hinkley Point C is approved BBC News (20/3/13)
Britain’s Plans for New Nuclear Plant Approach a Decisive Point, 4 Years Late New York Times, Stanley Reed and Stephen Castle (15/3/13)
Nuclear power plans threatened by European commission investigation The Guardian (14/3/13)
New Hinkley Point nuclear power plant approved by UK government Wired, Ian Steadman (19/3/13)
Renewable energy providers to help bear cost of new UK nuclear reactors The Guardian, Damian Carrington (27/3/13)
Europe backs Hinkley nuclear plant BBC News (8/10/14)

Information/Reports/Journal Articles
Environmental permitting of Hinkley Point C Environment Agency
NNB Generation Company Limited, Radioactive Substances Regulations, Environmental Permit Application for Hinkley Point C: Chapter 7, Demonstration of Environmental Optimisation EDF
Greenhouse Gas Emission of European Pressurized Reactor (EPR) Nuclear Power Plant Technology: A Life Cycle Approach Journal of Sustainable Energy & Environment 2, J. Kunakemakorn, P. Wongsuchoto, P. Pavasant, N. Laosiripojana (2011)


  1. Compare the relative benefits of a construction subsidy and a subsidised high strike price from the perspectives of (a) the government (b) EDF.
  2. What positive and negative externalities are involved in nuclear power generation?
  3. What difficulties are there in valuing these externalities?
  4. What is meant by catastrophic risk? Why is this difficult to take account of in any cost–benefit analysis?
  5. What is meant by a project’s return on capital? Explain how discounted cash flow techniques are used to estimate this return.
  6. What should be taken into account in deciding the rate of discount to use?
  7. How should the extra jobs during construction of the plant and then in the running of the plant be valued when making the decisions about whether to go ahead?
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Ore struck in Goa

My son Andrew Sloman (see also) is currently in Goa. My wife Alison and I went to visit him over half term – our first trip to India. Goa is a beautiful state, with wonderful beaches, fantastic food and perfect weather in February. But inland from this tourist haven lies an environmental disaster caused by the open-cast extraction of iron ore.

This tiny state by Indian standards produces more than 60% of India’s iron ore exports. Whilst, along with tourism, the iron ore industry has been one of the largest contributors to the Goan economy, its environmental footprint is massive. Deforestation and water and air pollution are just three of the environmental externalities.

So should a cap be placed on the amount of iron ore that is mined? Should the industry be taxed more heavily? Should tough environmental standards be imposed on the industry? Or should it simply be allowed to continue, given its large contribution to the Goan economy? Or, at the other extreme, should the industry be closed? The linked article looks at some of the issues. Try to identify, as an economist, what information you would require in order to come to a conclusion to these questions.

Greens’ shout for cap on iron ore mining falls on deaf ears Times of India, Paul Fernandes (28/2/12)


  1. What negative externalities are involved with the Goan iron ore industry? Are there any positive externalities?
  2. What difficulties are there in measuring the negative externalities?
  3. How would you set about doing a cost–benefit analysis of (a) expanding the Goan iron ore industry; (b) shutting it?
  4. Explain the following: “The net present value of the opportunity cost for 25 years at 12% social discount rate of giving it up is greater than its environmental cost by Rs 14,449 crore, the report states.” (A crore is 10 million and Rs is the symbol for an Indian Rupee, where £1 = approximately 78 rupees.)
  5. What difficulties are there in attempting to take distribution into account when doing a cost–benefit analysis?
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What Al Gore doesn’t understand about climate change

Al Gore’s contribution to the global climate change debate is not in question and he has, along with the IPCC, been awarded the 2007 Nobel Peace Prize for his work in raising awareness. If you haven’t seen his film “An inconvenient truth” then do get hold of the DVD – it may just be the most interesting PowerPoint presentation you will ever see! However, does he really understand the nature of the debate? The article below suggests that he has not yet taken account of the most fundamental trade-off in dealing with climate change – the trade-off between our own quality of life and that of our descendants in the future.

Save the earth in six hard questions MSN Slate (22/10/07)

1. Explain what is mean by a trade-off “between the quality of our own lives and the quality of our descendants’ [lives]“.
2. What is meant by the term ‘risk-averse’ and how is this relevant in the climate change debate?
3. Consider the questions raised by the article. Discuss how relevant the conclusion reached is in the light of these questions.
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