HOPE NOT HATE, a charity that combats extremism, published a report on November 28th purportedly revealing a mass outbreak of online hate-speech after the murder of Jo Cox, a Labour MP, a week before the Brexit referendum in June. In the month after the killing at least 25,000 people sent more than 50,000 tweets celebrating her death or praising her murderer, Thomas Mair, Hope Not Hate said.

Britain’s largest newspapers leapt to publish the shocking findings. The story was shared far and wide. Angela Eagle, a Labour MP, cast its conclusions as “staggering and appalling”. The news struck as Britain was coming to terms with an increase in hate crimes. (This week a man stabbed a passenger on a London train reportedly while shouting anti-Muslim slogans.) The discovery that such hateful attitudes were not isolated, and that tens of thousands of members of the public were willing to voice them openly, was deeply troubling.

Yet the story was wrong. An investigation by The Economist has found that Hope Not Hate misrepresented the findings of its own report when first releasing it to the press. The report itself gave a confusing impression of the number of tweets that celebrated Ms Cox’s murder. We estimate that, in reality, of hundreds of thousands of tweets mentioning the MP by name, the number that celebrated her death was at most 1,500, and probably much lower.

Although press coverage of the story appeared to misread the report, that is not entirely the fault of journalists. The claim that 50,000 tweets celebrated Ms Cox’s death or praised her killer comes from the first paragraph of a press release sent out by Hope Not Hate ahead of the report’s publication. It does not appear in the study itself, which found only that a “majority” of the tweets, which related to both Ms Cox’s murder and the Brexit referendum more broadly, “related to specific calls for violence” (a term that is not defined).

Hope Not Hate admitted that its initial press release was incorrect and said that it was later changed. The charity referred us to the study’s authors, Imran Awan of Birmingham City University and Irene Zempi of Nottingham Trent University. Mr Awan agreed that newspaper headlines had oversimplified the study’s findings. Even so both authors retweeted articles repeating the press release’s false claim.

In their study, entitled “Jo Cox ‘deserved to die’”, Mr Awan and Ms Zempi examine a sample of 53,000 tweets with hashtags related to both Ms Cox’s murder and the Brexit referendum. The total number of tweets on these subjects during the period was significantly more than 53,000; the authors appear to have selected their sample by narrowing their search using hashtags including #refugeesnotwelcome and #DeportallMuslims.

The report does not say what proportion of the 53,000 sample tweets related to Ms Cox’s murder, and what share concerned Brexit more generally. When The Economist asked the authors for help, they declined to share their data with us, citing death threats they said they had received since the report’s release. So we undertook our own analysis, examining tweets from June and July that included the terms “Jo Cox” or “#JoCox”—some 341,000 unique messages. Of a random sample of 800 of these, none was celebratory, and just four seemed to be derogatory toward Ms Cox, criticising her support for Syrian refugees, for instance. From this, simple statistics suggest that the true number of tweets cheering the politician’s murder would lie between 0 and 1,500. (The Hope Not Hate report reproduces about 30.) Mr Awan notes that our sample did not include tweets that mentioned only the killer, Mr Mair; it is also likely that some tweets were deleted before our collection.

The archive of tweets was gathered by Martin Goodson and Rafal Kwasny, data scientists at Evolution AI, a London-based startup. They found the Hope Not Hate report had other claims that seemed overdone. For example, it said a “key theme” on Twitter was the description of Mr Mair as a “hero”. In fact, many tweets containing the word “hero” were referring either to Ms Cox herself or to a pensioner who was injured while intervening to save her.

The authors point out that their search terms were broader than those used in our analysis, including terms related to Brexit and immigration. So for good measure, we also studied a random sample of 1,000 Brexit-related tweets collected by scientists at the University of Sheffield. Of these, we judged less than 1% to be xenophobic or worse. Multiplied by the millions of tweets about Brexit, this would add up to plenty of bile—even if you narrowed the sample down using the most inflammatory search terms you could still probably generate a sample of 53,000.

Hope Not Hate’s mistake is to take xenophobic Brexit-related tweets (which are plentiful, though a tiny fraction of the whole) and add them to tweets celebrating the murder of an MP (which as far as we can establish were very rare) to make a single tally of hatred. It then compounds the error by focusing on Ms Cox in the report’s headline and the initial press release.

The authors write that Twitter “acts as an echo chamber, where hateful comments are reinforced and can impact upon wider community cohesion.” Here they are right—which is why it is important to debunk claims which are not properly supported, including their own. That a single person would celebrate an MP’s murder is terrible. Yet the public was led to think that such a reaction was widespread online. We do not believe that it was.