With more than two babies born every second, the arms on the world population clocks are whirling round so fast that no-one really knows how many people there are on Earth.
The United Nations' Population Division, which calls itself the Gold Standard for setting the figure, says the world's population will hit 7 billion some time Monday, but it admits the date is symbolic.
No-one can know this, the New York-based body said on its website.
But there are plenty of experts who do not agree with the UN body's prediction.
The US government Census Bureau's world population clock says the figure will not be reached until April next year. The private Population Reference Bureau, also based in Washington, says the magic 7 billion was passed weeks ago.
The International Institute for Applied System Analysis estimates the world population will not reach 7 billion until some time between July next year and January 2013.
The UN forecasts have a margin of error of at least 1 per cent, the population division says. Even if they are 1 per cent off, the magic figure could have been reached six months ago, or it could take another six months.
Because of the inevitable inaccuracies in all demographic statistics, UN experts say it is safer to estimate the figure could have been reached one year ago, or could take another year to get there.
The UN relies on census figures from the 193 member nations and the population statisticians say that even the world's best censuses have errors in the range of at least 1 to 2 per cent.
The population division, which has been making its estimates since the 1950s, says the error factor is why it reviews its figures every two years.
Under its current estimate, the world population should reach 8 billion on June 15, 2025, give or take a year.
Update: Philippines welcomes symbolic '7 billionth baby'
The Philippines welcomed one of the world's symbolic seven billionth babies Monday, after she arrived to a celebratory cheer at a packed government-run hospital.
Weighing 2.5 kilos (5.5 pounds), Danica May Camacho was delivered just before midnight Sunday amid an explosion of camera flashes in the delivery room at Manila's Jose Fabella Memorial Hospital.
She looks so lovely, the mother, Camille Dalura, whispered softly as she cradled her tiny baby.
I can't believe she is the world's seventh billion.
The baby is the second child for Dalura and her partner, Florante Camacho, who quietly stood in a corner wearing a white hospital gown as television crews and photographers crowded to get a shot of his daughter.
The parents and the baby were met by top United Nations officials in the Philippines, who presented the child with a cake.
There were also gifts from local benefactors including a scholarship grant for the child's study, and a livelihood package to enable the parents to start a general store.
Also on hand to witness the event was 12-year-old Lorrize Mae Guevarra, who the Philippines declared as its own symbolic six billionth baby in 1999 when the world reached that demographic landmark.
I am very happy to see this cute baby. I hope like me she will grow up to become healthy and well loved by everyone, said Guevarra, who is now in the sixth grade.
The United Nations named a Bosnian baby, Adnan Mevic, as the Earth's six billionth inhabitant on October 12, 1999. The secretary general at the time, Kofi Annan, was pictured in a Sarajevo hospital with Mevic in his arms.
The Mevic family is now struggling in poverty at their Sarajevo home, which is partly why no baby will be put in the global spotlight this time.
Danica May Camacho is one of several children in countries around the world being declared a symbolic seven billionth human.
It was hoped she would arrive at exactly midnight, but she was delivered two minutes early.
Health Secretary Enrique Ona said the arrival of the world's seven billionth baby also presented the Philippines with an opportunity to assess population related issues.
According to the UN Population Fund (UNFPA) State of the World Population Report, the Philippines is the 12th most populous country in the world with 94.9 million people.
China continues to have the biggest share of the population at 1.35 billion, followed by India at 1.24 billion.
The report noted that in many parts of the developing world, where population growth outpaces economic growth, reproductive health care remains a crucial issue.
UNFPA representative Ugochi Daniels said that while the Philippine population remains young, with people under 25 making up 54 percent of the total, they needed to be taught proper life skills and about sexual issues.
She said that while women were having fewer children globally, the overall population continued to increase.
While our world of seven billion represents a complex picture of trends and paradoxes, there are some essential global truths we observe, she said.
Conversely, there is no one global population outlook.
The UNFPA said 10 percent of girls in the Philippines aged 15 to 19 have started child bearing, with many of the young also increasingly vulnerable to HIV. (Agencies)