It's more efficient to go shopping when everyone else is shopping: This is one explanation for the rise of Christmas as a shopping season. Even many people who don't celebrate Christmas do a lot of shopping and gift giving during this season. At the other extreme, a "dead mall" is one of the dreariest sights of modern consumer capitalism. Let's see how a pleasant shopping experience is a network good.

a. Part of the pleasure of walking through a mall is the pleasure of seeing and being seen. When will you see more people at the mall: in the months before Christmas or at other times? So if you like seeing people, when will you tend to go to the mall? (This is an example of the "multiplier effects" so common in economics.)

b. When you were in high school (or perhaps middle school), you may have spent time hanging out at a mall. How was the mall like Facebook, MySpace, or other social networking Web sites?

c. Malls will spend more money on decorations and entertainment when they can spread this cost over a large number of consumers. Again, when will you expect to see more of these extra expenses: in the months before Christmas or at other times?

d. If Christmas is so great for malls, why don't they have Christmas every month, spending money on decorations and singers all the time? Of course, they try to do this with Easter and back-to-school and Valentine's Day, and so forth, but why do these attempts fail so miserably compared with the big success of Christmas? Answer in the language of network goods.