There were around 100,000 there, reckoned Rawiri Waititi. More like 22,000, said Winston Peters. \u201cA hell of a lot more than 35,000,\u201d said Shane Jones. Media estimates <\/a>ranged from 17,000 to 100k. Online sleuths rattled out their appraisals like Wall Street traders. A Ng\u0101puhi data nerd in Canada whose aunty was massaging tired marchers in Wainuiomata studied drone footage <\/a>and concluded 50,000 at least.\u00a0<\/p>\n At times such as these, the counts that tend to get repeated into calcified form come from the constabulary. They have no formal responsibility to stick a number on the tin, but their calculations are of critical importance \u2013 in managing resources, forestalling any dangerous overcrowding and so on. The official police estimate <\/a>just before 1pm on that Tuesday in November was 35,000. Four hours later, that was revised <\/a>up to 42,000.\u00a0<\/p>\n How, then, do they arrive at that number, with its polish of authority? Is there some fancy, cutting-edge tech they deploy in the cause? A crowd-size manual? A superintendent with special responsibility for estimate-ops? I filed an official information request to find out.\u00a0<\/p>\n The response is in, and if you were expecting something involving elaborate algorithmic mesh computations, you\u2019re going to be disappointed. Turns out they do it pretty much the way any of us might. \u201cThe technique to estimate crowds when the event is occurring is usually by taking screenshots of streamed video from a wide range of sources and counting from that,\u201d wrote inspector Marc Paynter in response. \u201cThis includes publicly available video and photos.\u201d<\/p>\n There isn\u2019t even a policy.\u00a0 \u201cThere are no documents or written guidance or methodology on estimating crowd size used by police,\u201d he said. \u201cUsually crowd size is estimated by aspects such as the capacity of a stadium, previous events of a similar nature, number of entries sold by the organisers etc. Even the weather forecast will impact the turnout to many events.\u201d<\/p>\n A request for any correspondence relating to the estimation of the numbers attending the h\u012bkoi was rejected on the grounds that it \u201cwould be likely to prejudice the security of New Zealand\u201d or cause \u201cprejudice to measures protecting the health or safety of members of the public\u201d.<\/p>\n Paynter did note that an estimation of likely attendance had been made in advance of the h\u012bkoi, given the need to \u201cdetermine resources as part of the planning process\u201d. That figure, arrived at in late September, was 15,000-25,000 \u2013 \u201cbased on previous events\u201d, he said. \u201cThe Auckland Harbour Bridge attendance was used as an indicator of crowd size to predict the Wellington crowd size.\u201d<\/p>\n There was no mention in the police response to a \u201cformula\u201d described in remarks attributed to a police spokesperson in an RNZ report <\/a>from December. They\u2019d said then: \u201cA formula of 1.5 people per square metre resulted in an estimated crowd size of nearly 42,000 people.\u201d<\/p>\n That approach \u2013 of counting the crowd density in a small area and extrapolating out \u2013 is often described as the Jacobs\u2019 Method<\/a>, and dates from the 1960s. It\u2019s not without its uses, but it\u2019s a crude measure, and limited in its efficacy.\u00a0<\/p>\nThe crowd at parliament for the h\u012bkoi (Photo: Hagen Hopkins\/Getty Images)<\/p>\n