Bent Flyvbjerg (Professor at Säid Business School, University of Oxford) on 2-3 billion sustainable population (2017): “From an anthropocentric perspective, to calculate the Earth's ideal population size, one would first need to establish an ideal benchmark for what we think is a good life, and calculate the resources it takes to sustain that lifestyle. As a first approximation, let's take the French lifestyle as a benchmark. According to the Global Footprint Network's calculator, if all of humanity were to live like the French, we would need about 2.5 Earths to sustain that lifestyle. Any lifestyle that cannot be universalized to the rest of humanity cannot be just. Every newborn should be able to enjoy their fair share of the world's resources. Thus, to ensure the ideal population size so that everyone could enjoy a comparable way of life, taking the French lifestyle as our benchmark, we would need to reduce the world population to about 3 billion people (4.6 billion less than today's population). If, instead, we chose the lifestyle of people in the USA as the benchmark, then the world population would need to be reduced to 1.9 billion. It is unclear, however, that the American lifestyle is any better than the French, in terms of well-being. On the contrary: it looks like Europeans are faring better than Americans” (Bent Flyvbjerg quoted in Daniel Kolitz, “What is the ideal number of humans on Earth?”, Gizmodo, 28 December 2017: https://www.gizmodo.com.au/2017/12/whats-the-ideal-number-of-humans-on-earth/ .)