The first assumption was based on a remark by the United Nations secretary general, António Guterres, that the problem of sexual abuse was probably worse on the civilian side of the organization than within the peacekeeping forces. Mr. MacLeod concluded that this meant there must be at least 312 victims of the non-peacekeeping staff — 311 plus 1 — but to keep his “estimate” conservative, he put the number at 289, to arrive at an even 600 for the year. Needless to say, that kind of rounded guess based on an offhand statement is unlikely to be reliable.

From there, Mr. MacLeod estimated that only 10 percent of the assaults were actually recorded, a figure he said was based on reporting rates in the United Kingdom, to arrive at a figure of 6,000 victims annually. But because the United Nations doesn’t have good (or possibly any) data about the rate at which victims report assaults by its staff, there’s no way to know if that was the right multiplier to use.

Then, to arrive at an estimate for the decade, Mr. MacLeod assumed that 2016 was a representative year, so he multiplied 6,000 by 10.

Presto: 311 becomes 60,000.

By the Numbers

In Mr. MacLeod’s telling, he always intended his memo to be an advocacy statement rather than what he called “peer-reviewed” statistical analysis — essentially a way to say “here is a problem that is very large and very bad” (my phrase), with digits instead of words.

The problem is, that isn’t how journalists use statistics, or how the public consumes them.

Good journalists always try to check the provenance of the numbers we cite. But we aren’t trained statisticians, so we can’t necessarily perform independent checks of every figure experts provide to us. And sometimes numbers manage to enter the news ecosystem so quickly and pervasively that our fact checks can’t keep up.

After the Parkland school shooting, for instance, you may have seen the viral statistic that America had experienced 18 school shootings already this calendar year.

In fact, it turns out, that number was misleading. It came from Everytown for Gun Safety, a gun-control organization, whose definition of “school shootings” is far broader than the common understanding of the term. It counts every time a person fires a gun in or near a school building as a “school shooting,” including a suicide in Michigan that took place outside a shuttered, empty school.