Bangladesh

Bangladesh, with 169.8 million people packed into 147,570 square kilometers, is one of the world's most densely populated nations at 1,150 people per square kilometer, yet its fertility rate has plummeted to 2.0 births per woman, below #5 Pakistan's 3.4. This demographic transition means growth is slowing to 1.1% annually, but the country's small land area magnifies challenges. Despite a median age of 27.3 years, Bangladesh's population is projected to peak at around 200 million by 2050, then decline, a trajectory far different from #6 Nigeria's relentless expansion. The density, 30 times higher than Brazil's 25 people per square kilometer, underscores the pressure on resources, even as improvements in healthcare have pushed life expectancy to 74.5 years.