One has to go out of one’s way in Denmark to find a synagogue to terrorize—the country has only a few thousand Jews. And one has to go out of one’s way in France to find a kosher market to attack.

The terrorizing of the grocery in east Paris, where Amedy Coulibaly killed four people in January, all of them Jews, was not a “random” act of violence, as President Obama oddly suggested. Nor was the February shooting of Dan Uzan outside a Copenhagen synagogue. Nor was there randomness last year in the killing of four people at a Jewish museum in Brussels or in the murder of a rabbi and three children at a Jewish school in Toulouse. A vicious anti-Semitism persists on the streets of Europe as well as in the Middle East and on the Internet.

Is anti-Semitism on the rise, as many claim? Anti-Semitic crimes and attitudes are hard to quantify, and data vary from region to region. Attitudes of the general population may become more benign while violence perpetrated by a hard-core minority increases. Some studies show that the number of anti-Semitic incidents declined in parts of Europe in the decade before 2013 but has shot up of late. In the United States, home to 70 percent of the world’s Jews, the number of anti-Semitic incidents has held steady or declined in recent years.