Corona Daily 102: Mexico’s Math Sleuths

Politicians, particularly the Presidents or Prime Ministers are rarely interested in giving accurate Covid-19 figures. High figures often reflect their handling of the pandemic. Donald Trump likely lost his presidency due to covid mismanagement. More heads will roll before the pandemic is over.

Excess mortality, the all-cause total deaths, is the tool journalists use to learn the scale of under-reporting. Last summer, BBC’s Persian service found out that Iran’s coronavirus deaths were three times the official numbers. In Nicaragua, a civic group counted 3,000 burials, when the official tally was 179. Russia classifies a death as covid only if post-mortem confirmed the virus presence. Different tricks are used to bring the real numbers down. Politicians are capable of flattening the curve for preserving their power.

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In Mexico, the covid mortality reports are produced, but released much later. And the daily count of deaths was always suspiciously low.

Laurianne Despeghel, 31, is an economic consultant. She graduated from the London school of Economics. Romero Zavala, 37, is a software developer. Both are fond of numbers. In May 2020, they met on WhatsApp, through a forum which was trying to track the real numbers of the covid toll in Mexico City. Both were keen to find the real picture.

In the middle of May, they got their first clue. “Mexicans against corruption and impunity”, a civic group, had obtained a set of leaked death certificates. Their authenticity was verified. The group estimated that the deaths were three times the official count.

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Mexico City, the capital of Mexico, has 52 civil registry offices to register death. Mexicans can simply type the number of the death certificate in the website and a copy pops up, a bit like typing a flight confirmation PNR number to get your air ticket on screen.

You need the info for each death certificate, Laurianne told Romero. Romero is an internet research fan. On a hunch, he wondered if a lazy programmer started the numbering from 1. Like lazy individuals who keep the password or pin as 1234. Surprisingly, that intuition was right. In each of the 52 registry offices, the first death certificate issued in 2020 was number 1. And the certificates were in ascending order. He simply needed to find the last number.

Romero wrote an algorithm. It would pretend to be a human asking for a copy of the death certificate. The true objective was to find the last number. Through repetitive trials (called the binary search), the algorithm found the latest certificate number for each of the 52 offices.

Romero discovered that between January and May 2020, Mexico City had 8072 excess deaths. The government had confirmed only 1832.

He did the same exercise for years 2019/2018/2017 and found that the officially reported numbers matched with the number of death certificates. What remained was replicating the method for the entire country.

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On 25 May, the findings were posted on a blog. That post went viral internationally. Two days later, when Romero returned to the civil registry site, he was greeted with a captcha, asking him to confirm “I’m not a robot”. The algorithm could no longer work. In subsequent months, Romero and Laurianne did their updates manually. By August, the excess deaths for the capital rose beyond 31,000. Under pressure, the city government posted in August its full database of deaths, scrubbing out the names and IDs. This would have normally taken two years.

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In March 2021, the federal government admitted the covid fatalities have been under-reported by at least 61%. On 29 March, the Health Ministry said the covid deaths exceeded 321,000, which at that point was second only to the USA.

Despite that, today the official figure for Mexico is only 217,000. The civil registry website is now improved. One must write the name and surname to get a copy of the certificate. The monthly updates have stopped.

Romero and Laurianne continue to look for new solutions. “I am now motivated by rage” wrote Romero on his blog post.

Ravi