Paris: Organisers and police at protests around the world often come up with widely different attendance figures, but why was the discrepancy at Sunday`s Paris march for "traditional family values" so huge?
According to the "Manif pour Tous" (MPT) group that organised the protest, 500,000 people attended the march through Paris, seven times more than the 70,000 figure touted by authorities in the French capital.
So who was right? MPT, the same group that waged an ultimately unsuccessful movement against same-sex marriage last year, admits its crowd counting method was "amateurish" and that it rounded up its final tally... by up to 100,000 people.
MPT activist Bruno Dary, who as former military governor of Paris used to play a key role in the security of the capital and surrounding region, was in charge of counting the number of protesters Sunday.
He says people were still setting off at the start of the march when others were arriving at the end. "The total route was 5.5 kilometres (3.4 miles) long, 30 metres (100 feet) wide, which equates to 150,000 square metres."
He estimated around three to four people were in one square metre, which if totted up comes to a total of between 450,000 and 600,000 protesters.
The problem with this method, according to an official at the CFDT union who has become an expert on crowd counting after attending protests for four decades, is that having three people per square metre is "completely impossible, unless you put them on top of each other."
The official, who wants to remain anonymous, says the union`s method is to post people at windows in several buildings along the route and count each line of protesters as it goes by.
"That`s also the method used by authorities and it`s the only one that`s worthwhile, along with a method that relies on aerial images," he says.Police told AFP that the crowd counting method they used on Sunday was the same as usual, and involved counting all protesters from two different locations.
Then over the next few days, they re-counted demonstrators based on footage of the march, and confirmed the final tally.
Police also said that the footage revealed protesters were not densely packed together throughout the march, casting doubt on the MPT crowd counting method.
An AFP journalist present at the protest added that while many activists were still departing from the starting point one hour after the demo began, they were not as densely packed as those at the head of the march.
Leaders of the "Manif pour Tous" group are keen to show their movement is not running out of steam.
After gay marriage, their target this time is medically assisted procreation techniques for lesbian couples and surrogacy -- both of which are illegal in France but they fear may be introduced in the near future.
Organisers recognised at a press conference Tuesday that their crowd counting method was "amateurish", pointing out that they do not have the same resources authorities have.
The three to four people per square metre estimate, they said, was actually only valid on the final part of the route where people were standing around to listen to speeches, and there were slightly fewer protesters on the rest of the march.
Based on these final estimates, organisers came to a grand total of 400,000 to 450,000 people, Dary told AFP.
"Then we rounded it up to 500,000."