BRUSSELS (AP) — Nearly 50,000 Russian men have died in the war in Ukraine, according to the first independent statistical analysis of Russia’s war dead.

Two independent Russian media outlets, Mediazona and Meduza, working with a data scientist from Germany’s Tübingen University, used Russian government data to shed light on one of Moscow’s closest-held secrets — the true human cost of its invasion of Ukraine.

To do so, they relied on a statistical concept popularised during the COVID-19 pandemic called excess mortality. Drawing on inheritance records and official mortality data, they estimated how many more men under age 50 died between February 2022 and May 2023 than normal.

Neither Moscow nor Kyiv gives timely data on military losses, and each is at pains to amplify the other side’s casualties. Russia has publicly acknowledged the deaths of just over 6,000 soldiers. Reports about military losses have been repressed in Russian media, activists and independent journalists say. Documenting the dead has become an act of defiance, and those who do so face harassment and potential criminal charges.

Despite such challenges, Mediazona and the BBC’s Russian Service, working with a network of volunteers, have used social media postings and photographs of cemeteries across Russia to build a database of confirmed war deaths. As of July 7, they had identified 27,423 dead Russian soldiers.

“These are only soldiers who we know by name, and their deaths in each case are verified by multiple sources,” said Dmitry Treshchanin, an editor at Mediazona who helped oversee the investigation. “The estimate we did with Meduza allows us to see the ‘hidden’ deaths, deaths the Russian government is so obsessively and unsuccessfully trying to hide.”

To come up with a more comprehensive tally, journalists from Mediazona and Meduza obtained records of inheritance cases filed with the Russian authorities. Their data from the National Probate Registry contained information about more than 11 million people who died between 2014 and May 2023.

According to their analysis, 25,000 more inheritance cases were opened in 2022 for males aged 15 to 49 than expected. By May 27, 2023, the number of excess cases had shot up to 47,000.

That surge is roughly in line with a May assessment by the White House that more than 20,000 Russians had been killed in Ukraine since December, though lower than United States (US) and United Kingdom (UK) intelligence assessments of overall Russian deaths.

In February, the UK Ministry of Defense said approximately 40,000 to 60,000 Russians had likely been killed in the war. A leaked assessment from the U.S. Defense Intelligence Agency put the number of Russians killed in action in the first year of the war at 35,000 to 43,000.

“Their figures might be accurate, or they might not be,” Treshchanin, the Mediazona editor, said in an email. “Even if they have sources in the Russian Ministry of Defense, its own data could be incomplete. It’s extremely difficult to pull together all of the casualties from the army, Rosgvardia, Akhmat battalion, various private military companies, of which Wagner is the largest, but not the only one. Casualties among inmates, first recruited by Wagner and now by the MoD, are also a very hazy subject, with a lot of potential for manipulation. Statistics could actually give better results.”

Many Russian fatalities – as well as amputations – could have been prevented with better front-line first aid, the UK Ministry of Defense said in an intelligence assessment published Monday. Russia has suffered an average of around 400 casualties a day for 17 months, creating a “crisis” in combat medical care that is likely undermining medical services for civilians in border regions near Ukraine, the ministry said.

Independently, Dmitry Kobak, a data scientist from Germany’s Tübingen University who has published work on excess COVID-19 deaths in Russia, obtained mortality data broken down by age and sex for 2022 from Rosstat, Russia’s official statistics agency.

He found that 24,000 more men under age 50 died in 2022 than expected, a figure that aligns with the analysis of inheritance data.

The COVID-19 pandemic made it harder to figure out how many men would have died in Russia since February 2022 if there hadn’t been a war. Both analyses corrected for the lingering effects of COVID on mortality by indexing male death rates against female deaths.