An estimated 380,000 people crowded Downtown on Wednesday for the Stanley Cup victory parade.
Or did they?
City officials said the figure stood between 380,000 and 400,000 people, but some news outlets reported more than 400,000 were there. Everyone agreed on one thing, however: It set a record.
“It’s the largest crowd we’ve seen in the city of Pittsburgh,” said Guy Costa, city chief operations officer.
Gauging the size of a crowd is an imperfect science. Pittsburgh officials used simple math to estimate and predict the size of Wednesday’s crowd. But sometimes the numbers are not what they seem.
“Estimating crowd sizes is a difficult problem, with typical methods producing notoriously unreliable estimates,” said Carnegie Mellon University statistics professor Christopher Genovese.
Moving crowds, like those Wednesday, are more difficult to measure and result in more imprecise estimates, Mr. Genovese said. Although Pittsburgh public safety officials relied on sidewalk square footage and crowd density to estimate Wednesday’s crowd, Mr. Genovese said looking at a crowd from an angle gives a misleading view of its density.
“Not all photos are created equal,” Mr. Genovese added.
Bias also can pose a problem. Mr. Genovese said the parties involved in estimating crowds often have a direct interest in skewing the final count. Research has shown that police estimates tend to be more reliable than estimates from event organizers.
The city used a simpler version of a tried and true method of quickly calculating crowd size. This method begins with the population density of a 10-foot area and then multiplies by the total square footage of the crowd. In densely packed crowds, a single person occupies about 2.5 square feet.
It’s easy arithmetic, but it does not always lead to precision.
Wednesday’s parade route was 12,000 feet long, with fans standing on the sidewalk 10 to 15 people deep. Factoring in people on side streets and in parking garages, and the 125,000 people who live and work in Downtown, the city predicted anywhere between 365,000 and 430,000 could show up on Wednesday.
The final figure, whether it was 380,000 or more than 400,000, is believed to have topped any crowd in Pittsburgh history. In 2009, police estimated 350,000 Steelers fans flocked to the Super Bowl victory parade, 100,000 more than the crowd at the Steelers’ parade in 2006. And in 2009, the Penguins’ Stanley Cup victory parade drew an estimated 375,000 people.
But what tipped the scales on Wednesday were the fans who filled the areas around Steel Plaza, One Oxford Centre parking garage and the BNY Mellon Center, Mr. Costa said.
The increase over the 2009 parade was because of the Penguins’ exciting and impressive season, Mr. Costa added.
But as mayoral spokesman Tim McNulty pointed out, estimates are just that — estimates, not precisely calculated figures.
“It all depends on the density of the crowd,” said Mr. Costa prior to the parade. “A lot of people in the buildings from the Golden Triangle will walk over during their lunch hour. A lot of workers will bring their families to work ... make a day of it.”
Predicting crowds before they form is an even bigger challenge. Carnegie Mellon statistics professor Steve Fienberg said the city most likely exaggerates the size of the crowd it expects. Prior to the parade, the city predicted between 350,000 and 400,000 fans would show up.
“I don’t have any sense of where 350,000 comes from,” Mr. Fienberg said. “For police, they’ve got to plan for more rather than less. It would be very bad if you planned for less security than you needed for a big crowd.”
Finnegan Schick: fschick@post-gazette.com.
First Published: June 16, 2016, 4:00 a.m.
Updated: June 16, 2016, 4:30 a.m.
