In his Oct. 18 Fact Checker column, “Clinton’s claim that 40% of guns are sold at gun shows and online is based on outdated data,” Glenn Kessler upbraided former secretary of state and current Democratic presidential candidate Hillary Clinton for misspeaking about gun background checks, citing two of our surveys, from 2004 and 2015, to support his contention. Our most recent survey, which has not yet been published, shows that Clinton’s larger point was right: Approximately 40 percent of gun transfers do not involve a background check.

Where Clinton erred was in saying that these transfers exclusively involve gun shows and online sales, when they also involve transfers such as retail sales, inheritances and trades.

The column, although correct, was a distraction from Clinton’s key message that in a country in which 90 people a day die by gunfire, all gun transfers should involve a background check. Based on our most recent survey, among the estimated 50 million-plus guns most recently acquired, roughly 20 million are in the possession of people whose legal right to have them is unknown. Are these guns more likely to be misused? Stolen? To make their way into underground markets? We suspect so, but there are no data that speak to the issue — in no small part because of a lack of federal funding for gun research. Clinton’s willingness to call attention to the unregulated transfer of firearms — whatever their source — directs attention toward the year-to-year toll of firearms, an issue she is right to insist that each of the presidential candidates address.

Deborah Azrael, Somerville, Mass.

Matthew Miller, Brookline, Mass.

Deborah Azrael is the director of research and Matthew Miller is the co-director of the Harvard Injury Control Research Center.