India's population is expected to stabilise at 1.8 or 1.9 billion by 2080 due to a falling fertility rate, the Indian Association for the Study of Population (IASP) said. Total Fertility Rate (TFR) is currently below the replacement level (the average number of children born per woman to stabilise population) at 1.9, IASP said. TFR was at 3.5 in 2000.