Overpopulation or Underpopulation?

Toby Ord Programme on the Impacts of Future Technologies

Oxford Martin School University of Oxford

Introduction Benefits of population

Costs of population How things might change

Pessimism about Population

Thomas Malthus, 1798 Paul Ehrlich, 1968

A more balanced view

• Population is not just a negative • It can also bring many benefits • We need to weigh the costs against the benefits

– There may be an imperative to limit population – There may be an imperative to increase it

• Laying a foundation for future discussions

Introduction Benefits of population

Costs of population How things might change

The Information Economy

Made from matter

Hammers

Each one must be laboriously made Must be laboriously made once Then can be very cheaply copied

Benefits one person who desires it Benefits all people who desire it

Value is independent of population More valuable with more people

Songs vs

Fundamentally just a pattern

The Information Economy

• Increasingly many goods are in the information economy – Novels, poems, films, songs, recipes – Science, inventions, designs – Software – All academic research

• With more people, we get more value from creating these • If you doubled the size of the population:

– We could get the same amount of these things with more free time – Or we could each get much more of these goods

Complex Goods

Made from iron

Hammers

Made in a smithy Made in a very complex factory

Could be made by a small population Requires a huge population to make

Computers vs

Made from a long list of exotic elements and components

Complex Goods

• We get a lot of benefit from complex technologies • Getting these with a much smaller population is either:

– Impossible – Or would have taken many more centuries

• Either way, we get these goods now because of population • What goods will we miss out on if we limit population?

The benefits for the new people

• ‘You are population too!’ – Is it good that you exist (ignoring effects on others)?

• What would we miss out on with 1 billion fewer people? – Current British population is 0.06 billion – Entire population who have ever lived in Britain from

prehistoric times onward is less than 1 billion – Was there something good about having all of this life and

activity that people strived for over the centuries? – Should we blithely give up things of this magnitude?

The benefits for the new people

• How to assess the value of a population?

Henry Sidgwick, 1874 Derek Parfit, 1984

The benefits for the new people

Look at the average wellbeing

Average

Good to add a life if it has greater than average wellbeing

Good to add a life if it has positive wellbeing

More likely to resist increasing population

More likely to advocate increasing population

Total vs

Sum up everyone’s wellbeing

Sidgwick’s preferred theory

The benefits for the new people

+ average + total

– average – total

The benefits for the new people

– average + total

– average + total

Better for some, Worse for none, Bad for none

The benefits for the new people

Average Total vs … Actual Necessary vs vs vs

• Total view sometimes implies an obligation to have more children

• But so do almost all other views • There is much more that can be said here…

Introduction Benefits of population

Costs of population How things might change

Limits

• There are many potential limits to population growth: – Food production – Fresh water – Energy – Atmospheric CO2

– Other natural resources

• In practice, these are not sharp cut-offs – But they can reach points of rapidly increasing costs

• We should mainly focus on the most limiting factor – If factor X limits us to 10 billion – and factor Y limits us to 15 billion – Then factor X warrants much more of our attention

Soft Limits & Hard Limits

• Are we near a limit on food production?

• Yes: – We can only just feed the current population,

and have little arable land left to expand

• No: – Meat production uses much more land per eater than vegetables,

so we could support twice as many people if we ate less meat

Soft Limits & Hard Limits

• Both are right in a sense – With business as usual, global food shortages may soon occur – With sensible management, they won’t

• We are not near the hard limit on food • We are near a soft limit • We should start thinking of ways to change behaviour

Distribution of Population

• Conditions in different countries vary greatly • The old population was not spread evenly • The new population will not be spread evenly • These factors combine to complicate things greatly

– Political upheavals – Migration – Regional shortages – Uneven power

• Need to be very careful about our intuitions

Introduction Benefits of population

Costs of population How things might change

Technological Change

• Erlich was wrong when he claimed: – ‘In the 1970s hundreds of millions of people will starve to death in

spite of any crash programs embarked upon now.’ • Green Revolution

– High yield cereals, irrigation, fertilizers, pesticides – Increased wheat yields per hectare by a factor of 3 – Norman Borlaug estimated to have saved > 200 million lives

Technological Change

• Technological changes could expand limits – Genetic engineering of crops, or new farming methods such as

aquaculture may ease food limits – Cheap, clean energy would relax many limits at once – In the long run… colonizing other planets

• Technological changes could increase benefits – Moving more things into the information economy – Developing new complex goods

Social Change

• If we could cooperate better, we could greatly expand many limits:

– Eating less meat – Using less water – Using less CO2 – Using less energy

• Could double all of these limits with little real cost…

Conclusions

• Questions about population targets are very serious and require a sober discussion

– The benefits must be weighed against the costs – It is possible to have underpopulation with an imperative to

increase our population

• Information goods and complex goods are two key reasons to have a higher population

• The intrinsic value of the new people is a third reason • We must distinguish between hard and soft limits • There could be great benefit in overcoming the limits with

technological and social change

Questions? Comments?

toby.ord@philosophy.ox.ac.uk