An Irishman's Diary

Think of a number. Double it. Now multiply the total by the square root of pi, and add your age plus your weight in grammes. Congratulations. If you did that correctly, you have arrived at an estimate of the number of people who turned up at that march or protest rally you just organised.

Of course it has to be vaguely plausible, based on visual impressions. But that’s not hard. Most people lack the capacity for computing large numbers. So at worst, you’ll be caught up in a game of crowd-estimate tennis, whereby your opponents bat the number back with reverse spin and you have to work a bit on the return.

Even then, though, chances are that the rally – pun more-or-less intended – will end with the media reporting your estimate, if only as a claim. The average journalist has, after all, chosen a profession in which words are paramount. Beyond the skills needed to calculate the mileage expenses for a round-trip from Dublin to Kerry, numeracy is probably not his or her forte.

As with most things, technology is catching up with fictional crowd estimates. There is now an app for that too, inevitably. But you still have to feed it certain data: the area of the rally, crowd density, average person-size, etc. Which data have always been available. So technology probably won’t end the mythology either.

Long before the smart-phone, in fact – since at least the 1960s, when mass protests were fashionable – people-counting has been pursued as a science by a determined few. Refinements along the way included the realisation that a college campus protest may be denser – in terms of spatial distribution, I mean, not intelligence – than the average.

Or as one US sociologist put it: “If a crowd is largely coeducational, it’s conceivable that people might press closer together just for the fun of it.” But in general, the leading American exponents work on the basis of allocating 2.5 sq ft per person to a tightly packed crowd, with more generous allocations for those further from the action. They then break the attendance into sections according to density. After that they measure the ground space covered by each.

The message, if you’re planning a mass protest, is that it’s probably best to avoid simple geometric spaces, like squares, that can be easily measured.

For a march, a narrow, winding route, with lots of side streets, is ideal. Not only does it allow multiple entry points. But if the rally at the end is sparsely populated, you can always say that many of the crowd pealed off en route. By including everyone who was milling around the fringes, you may also plausibly claim that the entire population of a city centre attended some or all of your event.

This doesn’t just apply to protests, by the way. The inclusion of multiple fringe-millers can be the only basis for the estimate of the crowds at Dublin’s biggest annual gathering: the St Patrick’s Day parade. Attendance at which is rarely said to have been under 500,000, but has been known to rise to 700,000 in good weather.

The half-million-plus attendance has long ago entered Patrician folklore, like the banishment of the snakes, except taken seriously. This even though the numbers that could be meaningfully said to watch the parade are limited to seven or eight rows of people on either side of a 1.5 mile route. However generously you count the heads, it still gives you plenty of change out of 100,000.

O’Connell Street, the parade’s traditional focal point, is in general a useful guide to crowd size. It’s a simple space: 500 metres long by an average 47.5 metres wide, giving an area of 23,750 sq m. So imagine having the entirety of it available for a rally.

Let’s assume the Americans’ 2.5 sq ft per person is too generous by Irish standards. Let’s even assume that our crowd is composed entirely of frisky students with drink taken. Thus, shrinking the average personal space to half a square metre, we would still struggle to squeeze 50,000 into Dublin’s greatest thoroughfare. That’s with both carriageways filled, plus footpaths, central meridian, trees, and statues, including the statue of O’Connell himself.

There, incidentally, was a man who knew something about hyping crowd figures. Cunningly, he held his monster marches in places that didn’t lend themselves easily to calculation. Hence the numbers said to have attended his greatest meeting – at the Hill of Tara – which have been put variously at 100,000, half a million, a million, a million and half, and whatever he was having himself.