I was worried for a while that I wasn't going to get any trick or treaters -- usually the very smallest kids will come around before dark, and I don't think I saw any before 7pm. And even when they did arrive, I had to leap out and ambush them; my apartment is part of an old victorian, so the front door leads into a vestibule. They'd usually arrive at the front door and murmur to each other rather than come inside, so I learned to listen for it and bring the candy out. But I ended up getting about 20, so the ritual of Halloween has been fulfilled.
ETA: I had a few latecomers who looked suspicously like SJSU freshmen (the dorm is about a half block from my house), but I did not begrudge 'em the candy.