The United States Census takes a census every 10 years. In the most recent census in 2020, the US population had grown by 7.4% in the past decade. This is contrast to some developed nations whose populations are declining, though population growth in the United States has slowed and the 7.4% is one of the lowest-ever decade-on-decade growth rates ever recorded. Recently, US fertility has hit record lows though it is still not as low as countries like Japan, Italy, Spain, and South Korea. Immigration to the United States is a significant source of population growth, especially in contrast with countries like Japan.