In a prior post Fermi Problems are Quadrature Problems we worked through the classic Fermi problem "how many chocolate bars are eaten each year in the United States?" twice - once as a naive one-point estimate (~40 billion bars/year) and once as a refined 4×4 age-by-season quadrature that preserved the age/season interaction (~44 billion bars/year). Both estimates hovered in the same order of magnitude, which was satisfying but also unfalsified: we worked from first principles and back-of-the-envelope estimates. No published, macroeconomic data from the real world went into the estimates.

This post is the falsifiability check. It …

Here's a Fermi problem you'll run into sooner or later, usually in a job interview, sometimes over drinks with someone who wants to see how you think:

How many chocolate bars are eaten each year in the United States?

The provenance goes back to Enrico Fermi's Chicago physics classes, where he'd ask students to estimate the number of piano tuners in the city, or the width of a nail's head in miles, or anything else where the point wasn't the number but the decomposition. That habit of mind has since been laundered through McKinsey and Google into the standard interview …