The Trolley Problem

The trolley problem is a thought experiment in ethics. The general form of the problem is this:

You see a runaway trolley moving toward five tied-up (or otherwise incapacitated) people lying on the tracks. You are standing next to a lever that controls a switch. If you pull the lever, the trolley will be redirected onto a side track, and the five people on the main track will be saved. However, there is a single person lying on the side track. You have two options:

Do nothing and allow the trolley to kill the five people on the main track. Pull the lever, diverting the trolley onto the side track where it will kill one person.

Which is the more ethical option?