You're on a gameshow. The host walks up to you in his plaid jacket and tells you there are twelve doors. He also explains that doors one through eleven have $1,000, and door twelve has over ten times as much money, $11,000. You don't have to guess. He tells you how much is behind each door up front. Now, which door do you pick?
Wait! Before you go off half-cocked and pick number twelve you need to be aware of one small fact: Lots of other people are playing the same game at the same time, and no matter what door you pick, you'll split the money with everyone else who picks the same door. Sure, you can pick twelve, but it's a safe guess that everyone else will, too. Is it better to pick the same door as everyone else and split the big pile of cash, or try for one of the other doors and get a smaller pile of cash all to yourself? The first question out of your mouth will probably be, "How many other people are playing?" The answer: "Nobody knows ahead of time."
This is the decision faced by publishers when deciding on a release date. They can pick the sales-rich Christmas season and fight over a massive pile of cash with everyone else, or they can release some other time and fight over a smaller pile of cash against a smaller group of games. Numbers are hard to find, but verbal lore suggests that retail sales during the Christmas season constitute nearly half of the yearly sales. That is, you'll sell as much during the Christmas season as during the other eleven months combined.
Yes, we're talking about Christmas during the month of August. No, I'm not one of those people who is always trying to start the season earlier each year. I'm talking about Christmas in August precisely because it's a nice long ways away and we can get a clear-headed view of things.
It's actually a lot more complicated than my game show example because gift cards, returns, and shoppers who were gifted money will create a secondary sales surge in January. But after that dies down there is a big slump as people start getting their post-Christmas credit card bills and snap out of their mad spending stupor. But if we don't want to be drawn into a vortex of advanced accounting theory we can just simplify things by assuming that the December sales equals roughly eleven regular month's worth of business. Those kind of sales would look attractive to anyone. It's possibly better to be the tenth most popular game in December than to be the top seller in May. Why kill yourself trying to be the best when you can be mediocre at Christmas and do just as well?
But it's not as simple as that, because the money isn't split evenly, and neither is the risk. There are only so many games a reviewer can play in a given span of time. During the summer drought, we have lots of time to pick apart each game and talk about it in detail. During the holiday glut, you could plow through a game every few days, dash off paper-thin reviews, and still not come close to keeping up with the new releases.