Dr Gibson hands out a tough quiz in the ‘comments’ thread of Jacques’s latest post on comparative advantage:

Quiz: last year I earned no money from writing. This year I expect to make $5,000. By what percentage will my writing income have risen?

Jacques is stumped. I am too, but I think I’ll take a stab at it anyway. The worst that can happen is that I’m wrong, right? Warren, by the way, has a PhD in engineering as well as an MA in economics, so math is his forte (he is also the math reader for Econ Journal Watch).

I speculate that the percentage of his writing income has risen by 100%. I don’t see how it could be anything else. If you start out at zero, then even if Warren only made $1 this year an increase from $0 to $1 would have to be 100%, right?

Am I right? I need help.

Digression: Jacques is right that the Romans got along fine without the zero, but that’s not saying much. Here is Tocqueville:

If the Romans had been better acquainted with the laws of hydraulics, they would not have constructed all the aqueducts which surround the ruins of their cities – they would have made a better use of their power and their wealth. If they had invented the steam-engine, perhaps they would not have extended to the extremities of their empire those long artificial roads which are called Roman roads. These things are at once the splendid memorials of their ignorance and of their greatness. A people which should leave no other vestige of its track than a few leaden pipes in the earth and a few iron rods upon its surface, might have been more the master of nature than the Romans.