The incident was classified by D.C. police as an assault with intent to rob. It suggests that for whatever reason, property was not taken. It occurred just after midnight on July 23, in the heart of one of downtown Washington’s most popular dining and entertainment area.

The would-be robbers approached their victims in the 500 block of Seventh Street NW. One had a knife. As recounted by police, at least one of them gave the curt order: “Give me what you got.”

In a report released Friday, D.C. police said they made eight arrests in the incident. All those arrested were teenagers. One of them was 18 and classified as an adult. The others ranged in age from 13 to 16.

Robberies and incidents such as the one that occurred July 23 in the downtown area are the principal violent crime reported in the District. More random than homicide, robberies are often considered to be an accurate barometer of the safety and security in a city.

In addition to any loss in cash or possessions, being confronted at knifepoint with a demand for property may often have an enduring psychological effect, experts say.

The most recent D.C. police figures, compiled only two days from the end of July, indicate that the total number of robberies in the city is less than in the same period last year. The figure through July 29 of this year was 1,770, and the corresponding number from last year was 1819.

The decline is about 3 percent.

The total is composed of robberies involving guns, and all other types. Robberies at gunpoint are likely to have the strongest effect on victims and on their overall sense of security.

As of July 29, the number of robberies with guns remained higher in the District than in the corresponding period of 2015.

But the figures may be read to indicate that progress is being made.

From Jan. 1 through April 15, the number of gun robberies was listed by police as 377. The corresponding figure for last year was 243.

That is an increase of 55 percent in the number of gun robberies in the first 3 1/2 months of the year.

But when calculated over the first seven months of the year, there is a sharp decline in the percentage by which this year’s gun robberies exceed those of last year.

Police figures listed 742 gun robberies this year through July 29, compared with 664 in the corresponding period of last year.

The increase is about 12 percent, far smaller than the 55 percent figure from the first half of the seven-month period.

However, an even closer look at the figures raises questions.

The number of gun robberies for the year so far is about twice the number of gun robberies in the first 3 1/2 months. That suggests that the number of gun robberies has remained relatively constant over time during 2016.

Meanwhile, it appears that there was a sharp disparity between the number of gun robberies early last year and the number recorded through the end of July.

The number of 2015 gun robberies reported through July 29 is 664. That is substantially larger than the 243 reported for the first half of that period.

This suggests an explanation for the approach of the number of gun robberies so far this year to the number at the corresponding time last year.

It suggests that the number of gun robberies this year has remained relatively constant. But the number of gun robberies last year apparently rose sharply during the year.