PARIS World population will level off at around nine billion by 2070 before going into decline, according to a report in a British journal to appear Thursday, contradicting predictions from previous research.

The study in nature magazine gives an 85 percent chance that the global population will stop growing before 2100, while giving slim odds that the decline will be such that the population dips below present-day levels, AFP reported.

The study, led by three researchers: Wolfgang Lutz, Warren Sanderson and Sergei Scherbov, predicts that after peaking at nine billion in 2070, world population will tail off at 8.4 billion by 2100.

The figure is one billion lower than United Nations projections for the end of the century.

The latest research also predicts that the proportion of people over the age of 60 will jump from a current average of 10 percent to 34 percent, representing a global average even higher than that seen today in Western Europe.

The study suggests that an ageing population will be the norm for all world regions with the result that by the end of the century there will be proportionately more elderly people in sub-Saharan Africa than there are in Europe today.

But China and Southeast Asia, which currently have similar sized populations -- around the 1.2 billion mark, -- are expected to evolve differently due to falling fertility rates hitting China sooner.

The result is expected to give China a 700 million person shortfall compared with Southeast Asia by the middle of the century.