I posed this very question to one of my professors of economic development at MIT in the early eighties, ufff!!!!

An honest and well-reputed scholar, he kind of avoided giving a precise answer. He said that the population size is not a control variable to be adjusted; all we can do is influence its growth rate upward or downward for the population size to reach a certain magnitude gradually. This I considered a useful answer- but it did not address the notion of optimal size per se.

Nonetheless, the world and views on development have progressed considerably since then. An answer to the question nowadays would have to refer to sustainability, one way or another.

In my opinion, one answer could be that the optimal size of human population at the global scale would be one compatible with a long-term stable equilibrium of a dynamic equilibrium model of sustainable development. Concretely, the optimal size of the human population worldwide would be such that, based on the prevailing consumption and production patterns by humans and the implications from these, is compatible with the well-functioning of all ecosystems in the planet.

There are three caveats -at least- to this. First, this attempt to answer does not give an absolute size of population, but one that depends on the culture and technology behind the prevailing consumption and production patterns. At different periods, characterized by existing cultural and technological conditions, the size of the human population that would be compatible with long-run sustainability as considered, would be different.

Second, the size of the population according to this tentative definition, more than an optimal size, would be likely a maximum. To define an optimal magnitude, it would be necessary to establish additional criteria (i.e., to formulate a precise objective function to be optimized). For example, one may consider aspects of per capita availability of natural resources, or whether the capacity of mankind to be more resilient would be enhanced or deteriorated depending on the size of the population (once more, depending on prevailing infrastructures, modes of social organization, public governance, etc.).

And, third, a notion like this about the optimal size of population should be taken as a reference, for instance, to assess gaps on how far mankind is from attaining sustainability in the entire planet, not as representing a control variable to be adjusted directly without due respect to ethics and human rights.

I would be glad to read more views on this!!!

Thank you Roberto for this crucial issue and your so well explained three premises

I couldn't have expressed them better. I agree i a100% with your points, especially when you state that there is not optimum.

I could add that in a large extent the maximum population may blimited by something that in the future can be the reaspons for conflicts and wars: Water, although it is dangerous to make predictions based om our actual knowledge.

It always comes to my mind the words on Thomas Malthus the Britihsh economist that said that as populatiuon grows more rapidly than food prodution, the only solution was wars, pests or other ways to decrese population. Fortunatelly, science found the way to produce more food based on fertilisants. Perhaps in the future,we can find the way to produce clean water that guaranties our existence perhaps for a couple of centuries.

Therefore, other than sustainability, for sure, another big player that may have the key for survival is science

Bapuji Maringanti

Nolberto Munier

Roberto Villarreal

I believe that we define the optimum human population as the number of people that the Earth can support without running out of essential resources like food, water, and energy. It's about having enough resources for everyone to live a good quality life, without harming the environment or causing shortages. Think of it like having a party: if too many guests come, there won’t be enough food, space, or drinks for everyone. Similarly, if the population grows too big, we might not have enough resources for all. The goal is to balance the number of people with the Earth’s ability to provide for us sustainably.

Optimum population will be the one with qualities that keenly consider the value and limitations of the mother nature.