The attack Wednesday in Alexandria, Va., is the 154th mass shooting this year, according to the Gun Violence Archive, a nonprofit organization that tracks information on shootings in the United States. On 165 days through the calendar year, that averages out to a little less than one mass shooting per day.

The shooting at the congressional baseball practice is in fact the sixth such incident this week. On Tuesday, eight people were shot in two incidents in Baltimore. On Sunday, nine people were shot during an incident in Chicago, four were shot at a lounge in Tennessee, and four teenagers were shot at an apartment complex in Houston.

The archive considers an incident a mass shooting if four or more people are shot, not including the shooter. Some definitions are broader: If the shooter is included in the tally, the number of mass shootings rises to 195. Some, however, are much more narrow: If a mass shooting is defined as four or more victims killed in a public location, excluding robberies and gang violence, the number falls to four.

Using the Gun Violence Archive's definition, the number of mass shootings has been ticking upward in recent years: Through June 14, there were 100 mass shootings in 2014, 135 in 2015, 142 last year and 154 this year.

This could be a function of the general uptick in violence that has been observed in some cities in recent years. It could also be partly a result of better reporting following increased public interest in mass shootings after a spate of the incidents in 2015.

Update: Later Wednesday, a UPS employee opened fire at a San Francisco package sorting facility, killing three people and wounding two others. The gunman then fatally shot himself. By the Gun Violence Archive's definition, it is the 155th mass shooting of 2017.