In a recent paper, Barro et al find that the probability of a country suffering a “consumption disaster” is about 1.7% per year. That sounds like an awfully scary number to me. For example, that means that over the course of a decade, there is about a 15% chance of having a disaster, and over the course of a typical lifetime (apx 80 years), there is a 75% chance of having a disaster.

I suppose that is large by today’s standards. But our preindustrial ancestors probably faced those kinds of odds each year, not each lifetime. I would love to see an estimate of such a number over time.

One point seven percent a year is a big number, particularly if one overspends on anything.

Compare 1.7% to .035%, the concentration of CO2 in the atmosphere. We are going to be asked to spend .017 times a hundred trillion (or is it ten trillion or a quadrillion?) every year to reduce carbon dioxide by a theoretical .002%, thereby theoretically saving Tonga’s beach cottages. This is change one can believe in.

OK, I might be off by a zero here and a decimal point there, but it seems to me that few others are using their calculators. Maybe you could give your students a lesson in scientific notation so they can keep up.

Or is it seventeen times pi times a trillion dollars times ten to the tenth divided by two? Whatever the number, we can well-afford it.