The most popular Jewish pastime, arguably, is our obsession with numbers and the size of the Jewish population, which, according to most recent studies, is in danger. The questions reverberate across Jewish boardrooms and dinner tables: How many Jews are there? Why aren’t there more of us? If two Jews fall in the forest, how many opinions will they have, and can we arrange for them to fall on each other in a way that might help one impregnate the other?