Production Possibilities Frontier

Q:

When we are required to draw the graph of the PPF, do we also indicate the midpoint at which the person/country/entity would produce and consume if no trade occurs? Or, is it enough that we indicate the amount of good produced on the axes and connect the dots?

A:

In general, I would say the latter of your two options, as long as you can assume that your PPF is a straight line (as done in Mankiw). Technically, you might not have enough information to figure out where the "no trade" production point is, since it depends on the preferences of the entity for one good over the other. While it is true that the figures in Mankiw show the no trade point to be at the midpoint of the line segment, there is no reason that this needs to be the case. If you look at the middle of page 48, the paragraph that starts with "Although these production possibilities frontiers..." should make this clear.