On Saturday, September 24, 2016 there was a demonstration in Mexico City organized by the National Front for the Family to protest a government proposal to legalize same sex marriage. This was in addition to many other similar demonstrations around the country. A news report about the event described it as planned between the Auditorio Nacional and El Angel de la Independencia in Mexico City. After the event, the organizers estimated 215,000 people attended while others estimated about 80,000. Various news organizations estimated “tens of thousands”. How can we reconcile a range of estimates like this?
Below is a CrowdSize study of Saturday’s march in Mexico City. We have two images of the event. The first is in front of the Auditorio Nacional and the second is looking east from the El Angel de la Independencia along the Paseo de la Reforma. The photographs show a very dense crowd at both locations.
If we perform a CrowdSize calculation for areas shown in these photographs, our total comes to 240,520 people; 80,500 people at the Auditorio Nacional location and 152,020 people on the Paseo de la Reforma. This method of estimating is open to interpretation to be sure but it is a calculation that we can perform for ourselves and it would probably compare favorably to what ever method the promoters and opponents of the event used to come up with their estimates.
The iPhone application CrowdSize, can perform area calculations for outdoor events and apply a density factor that gives us an estimate for the number of people within that area. Promoters and opponents of events as well as governments and the media can sometimes have a vested interest in discounting or exaggerating the popularity of demonstrations. With CrowdSize, we have a way to judge the popularity of events for ourselves.