At least five prominent critics of President Donald Trump received packages containing pipe bombs on Wednesday, and several others received similar suspicious packages that are still being investigated. Law enforcement officials speaking to The Washington Post described the bombs as acts of terrorism.

We don’t know much yet about the person or group sending the bombs, but while we await those details we can start to make sense of what it means that these recipients were targeted. To do that, it can be helpful to understand how these attempted attacks fit into the bigger context of American terrorism. While a few high-profile events dominate headlines, there are dozens of cases of terrorism annually in the U.S. — 65 in 2017, according to the Global Terrorism Database maintained by a group at the University of Maryland. Here are three ways Wednesday’s attacks do, and don’t, fit into the story of American terrorism.

This was a rare kind of attack

Terrorism is rare in the United States, and attempted assassinations of political figures (most of the people targeted this week were current or former politicians) are even more of a rarity.

We’ve written about the Global Terrorism Database before, and it’s not a perfect count of terrorist incidents. It’s based on media reports, for instance, and has transferred ownership over the years, so some spans of time have been filled in retroactively, after some media sources were no longer available. But it has tracked “the threatened or actual use of illegal force and violence by a nonstate actor to attain a political, economic, religious, or social goal through fear, coercion, or intimidation” since 1970, using a detailed coding system to categorize events. One of the ways the database categorizes incidents is by target — who or what the terrorists used force and violence against.

When a terrorist event is aimed at current or former politicians, it counts under the target category “Government.” And government is not the primary thing terrorists have gone after in America — not by a long shot.

Since 1970, businesses have been far more likely to be targeted in this country than government.

Meanwhile, assassinations, which the GTD classifies as “an act whose primary objective is to kill one or more specific, prominent individuals” are rarer still, accounting for 5 percent of all terrorist attacks between 1970 and 2017. In the last 48 years, there were 22 attempted political assassinations (18 of them unsuccessful) in the U.S.

Targeting business and private property rather than government buildings and politicians is practical, more than anything, said Erin Miller, the researcher who is in charge of managing the Global Terrorism Database. It allows the perpetrator to have an outsized impact on society without having to go up against the security resources of the government.

What’s more, in democracies like ours, people tend to engage in dissent against politicians or the government through protest, wrote Erica Chenoweth, a professor of public policy at the Harvard Kennedy School, in an email. “It’s really important to note that protesters tend not to become terrorists,” she wrote. “But rather people turn to terror in an attempt to compete with protesters.”

It’s not surprising that no one was hurt

The rarity of political assassination fits into a bigger trend, at least from Miller’s perspective. “There’s a large portion of the attacks in the U.S. that aren’t intended to hurt anyone. They’re aimed at property damage,” she said. They’re “intended to scare people.” Seventy-eight percent of all the terrorist attacks in the U.S. recorded by the GTD — and 83 percent of politically targeted attacks — caused no fatalities and no injuries. In contrast, about 35 percent of recorded terrorist attacks globally caused no physical harm.

That helps to create a reality where American terrorism statistics can be spun in a variety of ways, depending on what ideological point you’re trying to make. Take environmental extremist groups, such as the Earth Liberation Front that carried out 66 attacks recorded in the GTD between 1996 and 2009 — none of which killed or injured anyone. “If you’re concerned with the frequency of attacks, then this could be a serious problem,” Miller said. Whereas, if you focus on death and injury statistics, the same group can seem pretty benign.

Lone wolves are common

The U.S. has significantly less terrorism than many other countries. But our terrorism has also been less monolithic in its origins, Miller said. We have less, but it’s coming from a much more diverse array of actors and motivations.

For instance, consider Iraq, the top country for terrorist attacks in the GTD in 2017. Many terrorist attacks in a country don’t have a known perpetrator, but of Iraq’s 2,466 attacks, 47 percent were carried out by a single, organized group — the Islamic State. In contrast, the group that carried out the largest share of the 65 attacks in the U.S. that year was “white extremists” with 14 percent. No single group accounted for as big a chunk of American terrorism as the Islamic State did in Iraq, and even the white extremists were less a single, organized entity, than a loosely associated ideology.

While domestic terrorism in the 1970s was dominated by left-wing militants, the modern norm in the United States is to have terrorism committed by a small number of individuals inspired by ideology but not affiliated with any actual organization. “It’s almost a caricature, the amount of variation in what’s motivating people” to commit terrorism in the United States, Miller said. “Very rarely are we able to attribute to a formal organization.”

That doesn’t mean there’s no pattern to who is perpetrating terrorism in this country. A decade ago, then-Homeland Security Secretary Janet Napolitano’s office got into political trouble for a report warning about the rise of violent right-wing extremism, Chenoweth pointed out. Those are concerns that have since been echoed by law enforcement, a Cato Institute researcher and the Southern Poverty Law Center. And, indeed, a 2017 analysis by the National Consortium for the Study of Terrorism and Responses to Terrorism — the organization that manages the GTD — found that right-wing extremism had increased significantly this decade, making up 35 percent of U.S. terrorist attacks from 2010 to 2016 — compared to just 6 percent in the 2000s.

On the one hand, Miller said, the lack of organized, named, top-down terrorist groups could be contributing to lower levels of terrorism in the U.S. compared to other countries. On the other hand, though, this kind of terrorism is also difficult to investigate and stop, she told me. There’s not necessarily an organization to infiltrate and, of all the people inspired by a potentially violent ideology, it can be hard to figure out who will actually act on the incitement to violence. “It’s a pretty serious challenge for law enforcement and policymakers,” she said. “Especially in a country that values civil liberties the way we do.”