According to the UN's 2010 revision to its population projections, world population is projected to peak at billion in 2100 compared to 7 billion in 2011.  In 2011, Indian economist Sanjeev Sanyal disputed the UN's figures and argued that birth rates will fall below replacement rates in the 2020s. According to his projections, population growth will be only sustained till the 2040s by rising longevity, but will peak below 9 bn by 2050.  Conversely, a 2014 paper by demographers from several universities and the United Nations Population Division projected that the world's population would reach about billion in 2100 and continue growing thereafter.  One of its authors, Adrian Raftery, a University of Washington professor of statistics and of sociology, says "The consensus over the past 20 years or so was that world population, which is currently around 7 billion, would go up to 9 billion and level off or probably decline. We found there’s a 70 percent probability the world population will not stabilize this century. Population, which had sort of fallen off the world’s agenda, remains a very important issue."