Economics is often formally dened as being a social science dealing with the choices which humans make under conditions of scarcity and uncertainty. We'll examine the issue of uncertainty later in the course, so for now, let's take a look at this topic of scarcity, since it's so fundamental to what econ. is all about, really. We're introduced in this week's readings to the concept of opportunity cost. This is simply a recognition that, everywhere in life, if we do one thing then we by denition give up the opportunity to do another thing. And time is probably the ultimate opportunity cost, isn't it? If we define an opportunity cost as the value of something not chosen or given up, then the idea that "time is money" begins to take on a new relevance not just for the superrich, but for everyone. You've probably all heard statistics about the amount of time that the average American spends sitting in trafc, or at stoplights, for instance, and it can seem very distressing. This is time, after all, that can be spent productively, even if that production is the production of sleep! This is going to be one of the ultimate issues for researchers in many academic fields in the future, I think the issue of how to better utilize our time, which is, obviously, limited. Improvements in life span are one thing, but until further increases here are possible, how important is the value of one's time