Christmas decorations send some fifteen thousand Americans to the emergency room every year. When does the carnage peak? Photograph by David Hecker / Getty

At some point between Thanksgiving and Christmas, after the leftover turkey is gone but before the mail-order fruitcake arrives, many Americans engage in the annual ritual of putting up decorations. There is no data set on when most people embark on this task, but an existing record—the National Electronic Injury Surveillance System (NEISS), a U.S. Consumer Product Safety Commission database that tracks which products cause emergency-room visits in the United States—may hold the answer.

As it turns out, decorating for Christmas sends some fifteen thousand Americans to the E.R. every year. Presumably, more injuries occur as more people put up decorations, so a look at the hospital data from the past decade or so should reveal when most Americans are busy decorating. The NEISS data set, which spans from 2003 through 2013, includes about four thousand decoration-related E.R. visits, a comparatively small sample. The statistics indicate that around a fifth of all injuries involve Christmas lights, and about half involve non-electric decorations such as wreaths, trees, and ornaments. (Artificial trees, which occupy their own category, account for one in ten injuries.)

In the chart above, the days around Thanksgiving (in orange) mark the real beginning of injury season, though a little more than five per cent of hospital visits occur earlier in November, suggesting that some Americans may start decorating quite early. The E.R. is busiest between December 4th and December 7th, perhaps coinciding with the most popular decorating days. The activity then falls off steadily, with a substantial drop after Christmas (in red). There is another bump between New Year’s Day (in green) and January 5th, likely corresponding to the times that many people remove their decorations.

What do these injuries entail? Frequently (fifteen per cent of the time) they involve chairs or ladders. The NEISS database, which collects physicians’ case notes, corroborates my theory that many of the injured were busy hanging or removing decorations:

69Y M FELL FROM 12-15 FT LADDER HELPING A NEIGHBOR PUTTING UP X-MAS LIGHTS STRIKING HEAD

PT FELL OFF THE LADDER INTO THE BUSHES AT HOME AS HE WAS HANGING CHRISTMAS LIGHTS SUSTAINED A MOUTH LACERATION

PT WAS STANDING IN A CHAIR TAKING DOWN CHRISTMAS DECORATIONS STEPPED DOWN HEARD POP IN CALF CALF STRAIN 68YO F

Chair and ladder injuries peak on December 4th, providing further support for my timing theory. (There are smaller peaks after Christmas and on January 4th.)

The NEISS data reveal that another cause for concern is injury by ingestion, which contributes to eight per cent of E.R. visits. One-year-olds appear to be most susceptible; by the time a child turns four, the danger has subsided greatly. Still, not even middle-aged Americans are immune, as one doctor noted of a fifty-seven-year-old patient:

HABIT OF PLACING INANIMATE OBJECTS IN MOUTH AND TODAY BIT DOWN ON CHRISTMAS ORNAMENT BALLS INJESTED ORNAMENTS

As you cautiously hang your stockings, remember the good news: seventy-five per cent of the decorating injuries come before Christmas Day, so you’re almost out of the woods.