What is the minimum population needed to sustain me in a comfortable life in the US, in terms of the people who create and maintain infrastructure, goods and services? The combinatorial explosion of dependencies boggles my mind: for instance, I enjoy New Scientist, so its journalists and all their dependencies would have to be added in too. And so on…

In a 2008 New Scientist interview, environmental activist David Suzuki discussed how the maximum population our planet could sustain with “Western” lifestyles could be as low as 200 million. Could this number provide the goods and services necessary?

The “combinatorial explosion of dependencies” makes answering this question difficult. Do we assume that “comfortable” includes feelings of security given by access to good medical care, the protection by emergency services and armed forces, education and pension funds with their income drawn from the profits of the labours of multitudes?

Then there is the consumption of goods and services; how much is accessibility to choice part of the feeling of comfort? I like wine and live music, but I wouldn’t like either as much if I had no choice but to drink the same wine and hear the same orchestra all the time. There is also a moral point: should all those supplying one person’s comforts be able to feel the same level of comfort?

Recently, I saw a revision from three to 11 of the number of Earths that the present world population is depleting unsustainably. If the current human population of more than 7 billion were reduced by a factor of 11 and then reduced again to bring everybody up to a Western standard of living, then 200 million people looks a reasonable stab at an upper bound to the question of how many people are needed to sustain a comfortable life in the US… unless the letter writer feels comfortable with a more modest lifestyle than stereotypical US standards.

In the event of major population reduction and fragmentation, maybe by nuclear war, a much reduced population could maintain a wide range of internally traded production, expertise and services so long as they had electricity and were efficiently organised.

What is the minimum town size likely to have the range of retail goods and services, plus advanced medical facilities, that you may desire or need? In the UK, this is maybe in towns with a population of around 300,000, the size of Nottingham.