Century Initiative. Been living under a rock? Go check out who Mark Wiseman is, his relationship to Carney.
More importantly, they are talking over a time frame of 2100. Doubling the population over the course of 75 years is probably fine. The economy can handle it over that time frame.
I first learned of it here on HN, someone submitted it last year.
>The economy can handle it over that time frame.
What economy? Are you planning on finding jobs for tens of millions more people? One might say that you don't have enough jobs to go around as it is.
Population almost exactly tripled in the last 75 years, though.