Got it? Gang violence doesn’t count; nor does domestic violence, even when a whole family is slaughtered. And of course, such a tally excludes extremely public mass attacks like the Boston Marathon bombings or intensely private rampages like Saturday’s Brooklyn stabbings, since the suspects didn’t use guns.

That rankles Northeastern University criminologist James Alan Fox, who in the last couple of years has dissented from specially tailored tallies (such as ‘Mother Jones’) that insist mass shootings and spree killings are on the rise.

“Sometimes the criteria are arbitrary, sometimes they’re hard to apply, and it tends to be a little subjective,” Fox told The Times last week. “How do you classify what workplace shootings count and what don’t count?”

He says that his numbers (which count only shootings) show no big fluctuation: There are usually about 20 mass shootings a year that kill four or more people, many of which make no long-term splash with politicians or the media.

And for Fox, a casualty is a casualty.

“As far as people killed, does it matter if there’s two shooters, one shooter, it’s in a public place, a semi-public place, a private place, or in a home?” Fox asked. “Does it matter where there was some military motive?”