Crowd estimates are often wildly off base, analysts say
Where there are crowd counts, there are skeptics.
Last fall, academics and crowd-count analysts scoffed at the city's estimate that 3.2 million fans attended the Red Sox celebration. In 2002, the Big Dig's estimate of 800,000 people crossing the Zakim Bridge at its celebratory opening came under fire and was proven wrong. The 1995 Million Man March was said to be more like 400,000 men.
The Patriots' celebration earlier this month was no exception.
Boston police admitted the day after the Feb. 8 parade through Boston that their crowd count of "nearly 1 million" at the gathering was based on guesswork. No math. No formulas. The number came from the "collective opinion of all incident commanders," according to Boston Police Sergeant Thomas Sexton.
However, those who used formulas to devise estimates at the Globe's request came in with much lower figures.
"A million is a number that easily rolls off the tongue, [but] it is much harder to mobilize that many people, even for a celebration," said Clark McPhail, a sociology professor at the University of Illinois who wrote an award-winning book on crowds and assisted The
After analyzing photos of the parade, McPhail said, "It is hard to put more than 150,000 people along both sides of this parade route."
The accepted method for estimating crowd size is to measure the size of an area, determine how much of it is occupied, then measure the density of occupation. That method, which McPhail refers to as "the gold standard" for gaining an accurate crowd count, was devised by the US Park Police during the 1960s Vietnam War protests.
But on orders from Congress, the agency has since stopped reporting crowd estimates, largely after Louis Farrakhan threatened to sue when the police reported that only 400,000 participated in the 1995 Million Man March in Washington.
The only way of knowing for certain is to do a head count. Short of that, an estimate can be made based on the density of the crowd and the capacity of the route, or area people could fill.
Boston University professor Farouk El-Baz, director of the university's Center for Remote Sensing, said the maximum capacity of the entire parade route could get only as high as 600,000, with people standing 50 deep the entire route.
Using downloaded images of the parade route from the US Geological Survey, El-Baz and a research assistant estimated the parade route at 1.87 miles. They then examined digital photographs taken along the route, counted crowd density, and averaged the number out to, at most, 400,000 attendees.
"The problem is you guys in the press," El-Baz said. "We have several times suggested that when it comes to estimate of crowds, we cannot depend either on the organizers, who wish to make a very large political statement, or the police, who can either underestimate or overestimate depending on whether they support this thing or not."
In the case of a victory parade, El-Baz said, police could use an inflated number to justify overtime and strength.
"We really do need some way of getting a handle on this," he said. "It is not rocket science. It is a very simple operation."
The guesswork by police on a victory celebration like the Red Sox parade may have little significance in the long run, however, said an advertising executive.
"The value in having a lot of people or having a large estimate from a marketing or advertising point of view isn't as important as it would be for a political movement or a march," said Will Keyser, director of corporate communications for the advertising firm Hill, Holliday, which helped with the parade and produced the "celebrate responsibly" ads that were broadcast prior to the Super Bowl.
"For the sponsors of the parade, the value of being associated with it was as much for television as it was for the fan experience," he said.
Massachusetts Institute of Technology physicist Bill Donnelly, who publicly questioned the Big Dig's numbers for the 2002 Zakim walk, doubted the "nearly 1 million" figure for the Patriots' parade, but said he did not want to be a naysayer.
"To those of us who work with numbers, you kind of get to the point where you just leave it," he said. "But at the same time, the truth is the truth. It's a serious thing if people are just putting out any number. It means other things aren't being vetted that carefully. We'd love to have large numbers for the Red Sox and the Patriots, but there's a principle."
At any rate, trouble with numbers is not peculiar to Boston.
In the 1970s, the Chicago archdiocese estimated more than 1 million people attended a Mass said by the pope in Grant Park, which lies near Lake Michigan to the east, said McPhail. But a photographer who had shot the event got the park's dimensions, calculated its capacity, and demonstrated that more than 500,000 people would have had to be walking on the water of Lake Michigan to have accommodated a multitude of that magnitude.
"While the pope may have performed some miracles for the gathering in attendance on that particular day, their walking on the water was not one of them," McPhail said.
