The US has just registered a fresh low point in population growth since the Depression era. Its annual growth rate sank below 0.7 per cent in 2015-16, making it the lowest rate of growth since 1936-37. When the slowdown first began in the early 2000s, lower immigration growth rates were the main contributor to the decline. But as these levels began to rise again, another phenomenon started playing a bigger role: people started having fewer children. This, coupled with an ageing population, could lead the population growth rate to drop as low as 0.5 per cent by 2040, according to US Census population projections.