Rossing says there are certain common characeristics from the point of view of time and location to the incidents. He points to the fact that there are more incidents in areas where Jews and Christians mingle, such as the Jewish and Armenian quarters of the Old City and the Jaffa Gate.
There are an increased number at certain times of year, such as during the Purim holiday."I know Christians who lock themselves indoors during the entire Purim holiday," he says .... http://www.haaretz.com