New York (CNN) -- Synagogues firebombed and defaced by graffiti. Windows smashed at shops owned by Jewish merchants. Is anti-Semitism on the rise?
The FBI is investigating a rash of anti-Semitic attacks in northern New Jersey, including the attempted murder of a rabbi after incendiary devices were thrown at his home above a synagogue.
Rabbi Nosson Schuman suffered minor burns in the incident Wednesday at Beth El Synagogue in Rutherford.
It was the fourth anti-Semitic incident in the past month in Bergen County. On January 4, a Paramus synagogue was hit by an arson attack, and in December, two temples were vandalized.
No arrests have been made. "We don't know if we're looking at one person or a group of people," said Bryan Travers of the FBI's Newark division.
In November, vandals smashed windows at five stores owned by Jewish merchants in Middlesex County.
New Jersey Gov. Chris Christie condemned the recent synagogue attacks. "I will not stand for it, and we will summon all necessary law enforcement resources to identify and prosecute those responsible," Christie said in a statement.
The Anti-Defamation League, which catalogs anti-Semitic incidents nationwide, is urging law enforcement authorities to step up security around synagogues. It's offering a $2,500 reward for information leading to the arrest of those involved in the Bergen County attacks.
But Jewish leaders and scholars contacted by CNN could only speculate on why there is a surge in anti-Semitic incidents in the Northeast.
"This year, it did go up, but I'm not ready to draw any conclusions," said Ken Jacobson, the ADL's deputy national director.
But Jacobson said he was concerned about the spike in attacks in New Jersey. "The surge of these incidents in a short period of time in New Jersey is not a conventional kind of thing," Jacobson said.
The type of incident is also alarming, he said. A rabbi attacked in his home is far more worrying than a swastika scrawled on a door. "We are watching very closely," he said.
Economic insecurity and polarization "create the kind of atmosphere where people act out," he said.
According to a November survey by the ADL, 15% of Americans hold deeply anti-Semitic views; that figure stood at 12% in the 2009 survey.
In the poll, 19% of respondents answered "probably true" to the statement: "Jews have too much control/influence on Wall Street." The theme of the "miserly Jew," as personified by Shakespeare's Shylock, is common in anti-Semitism.
"There's a persistent economic theme of the Jew not just as miserly but as economically parasitical," says Derek Penslar, Samuel Zacks Professor of Jewish History at the University of Toronto, and author of "Shylock's Children."
In the 1930s, anti-Semitism was "visible, public and people did not try to hide it," Penslar said. "Jewish bankers were often accused of fomenting wars." Things are much better now, he added. "There seems to be a change in the United States in how Jews are accepted."
Penslar is not convinced that the economic downturn is the main cause of anti-Semitic attacks.
"Things were much worse in 2008 and 2009. I was expecting something then.
"My sense is more often than not what's happening now is related to Middle Eastern politics." Namely, the stalemate about Israel, Penslar says.
Mark Potok of the Southern Poverty Law Center cited FBI statistics showing an actual decrease in hate crime incidents against Jews during the current recession.
Nationwide, the FBI reported 887 such incidents in 2010, compared with 1013 in 2008.
"I don't think are any obvious explanations," Potok says. "It may be there is a small number of people who are attacking repeatedly, and that just says you have a few very active anti-Semites out there."