In this new decade, Australia is expected to add another four million to its population, as it did in the previous decade. We have the fastest-growing population in the developed world (1.5% in the year to June 2019), which is one reason for nearly 30 years of economic growth. More people means more stuff. It's driven by net overseas migration of about 250,000 a year, and when most live in Sydney and Melbourne, the prosperity comes at a cost in transport, crowding and property prices.