Moscow, Oct 1 (IANS/RIA Novosti): The population of the earth could grow to seven billion this month, up from just three billion fifty years ago, and may reach ten billion by 2100, the UN's population department says.

There is no precise information about when the world's population will reach this symbolic figure. The UN world population fund declared Oct 31 as the symbolic date to mark the event and is to hold a number of events to mark it.

The world's population grew slowly until reaching one billion around 1804. However, it only took another 125 years to double and growth was then exponential. The world's population then grew seven-fold in just two centuries. The world's population has doubled since the 1960's.

Most of that growth is taking place in developing nations; there are only three developed nations the US, Russia and Japan, among the ten most populous countries.

Specialists say the reason for this exponential growth is the so-called demographic crossover - the process in which society with a high birth rate and high death rate enjoys sufficient economic growth to turn into a society of low birth and death rates.

When society can afford modern medicines, the death rate falls radically, but the high birth rate continues, leading to high population growth. That high birth rate eventually declines due to the wider availability of contraception, and development of a pension system.

The UN forecasts that maximum growth will be in developing countries, which will make up 97 percent of the new growth up to 2050, up from 38 percent now. By 2050, 86 percent of the world's population will live in developed areas, up from 68 percent in 1950 and 82 percent today.