prior probability

Here’s one of our favorite John McCain stories, via this beautiful eulogy in The Atlantic by Todd S. Purdam: “When his North Vietnamese captors demanded the names of his flight squadron, McCain recited the names of the Green Bay Packers offensive line, knowing that the false information would suffice (for the moment) to end their abuse. ‘There’s no bar fight he will walk away from,’ his onetime political strategist John Weaver once told me.”

And when I lived in them:

1. Amsterdam (summer of 2011)
2. Cuernavaca (summer of 1989)
3. Los Angeles (where I grew up)
4. Ocho Rios (summer of 2012)
5. La Habana (spring of 2003)

Honorable mentions: Ponce, P.R. (1998-2009) and Viejo San Juan, P.R. (1993-1995)

We are reposting this tweet in memory of our favorite Latin American man of letters, the late Jorge Luis Borges, and in honor of our 50th birthday today. (Actually, I’m not 50. I’m really 18 with 32 years of experience!)

Also: Happy Paris Liberation Day!

What is “proof beyond a reasonable doubt”? Your guess is as good as mine! By way of example, consider the case of Paul Manafort, President Trump’s friend and former campaign manager who was tried in federal court earlier this month on 18 separate counts of bank and tax fraud. After asking the judge to define “reasonable doubt” and after four full days of deliberations, the jury in his case found him guilty on eight of those counts, but the jurors could not agree on a verdict for the remaining 10 counts. (In criminal cases, the jury’s verdict must be unanimous, so a hung jury occurs even if just one juror disagrees with the remaining jurors about the outcome.) The Manafort trial thus poses a deeper question. Why do verdicts have to be all-or-nothing, “guilty” or “not guilty”? In other words, why can’t jurors emit a Bayesian verdict instead of wallowing over the meaning of “reasonable doubt”?

We have blogged about this possibility before and have delved into the mathematical details of Bayesian voting in a previous paper of ours, which was published in the Criminal Law Bulletin (vol. 51, no. 3). In summary, rather than voting “guilty” or “not guilty,” jurors could instead keep a scorecard and score the evidence presented by the prosecution at trial. Each juror’s scorecard could be based on a ten-point scale, with 10 being the highest possible score (an open-and-shut case) and 0 being the lowest score (not even a scintilla of evidence in support of the prosecution’s case). So, for example, if a juror believes that the prosecution has proved its case beyond a reasonable doubt, the juror would assign a high score, such as a 9 or a 10, or if the juror thinks the case is too close to call, he could assign a 5. Accordingly, the jury’s “verdict” would consist of a numerical value–either the average value or the sum total of all their individual scores (I refer to this collective score as the “range verdict.”) Under this system, the prosecution would win a conviction only if the average value or sum total of the jury’s collective score exceeded some critical threshold value.

Via Reuters: “Inflation [in Venezuela] hit 82,700 percent in July as the country’s socialist economic model continues to unravel, meaning purchases of basic items such as a bar of soap or a kilo of tomatoes require piles of cash ...” (Hat tip: Alex Tabarrok, via Marginal Revolution.) Hey, but at least everyone is equal … equally poor, that is!

A bar of soap = 3,500,000 bolivars, or the equivalent of 0.53 USD.

This visualization of daily bus and rail rides in London is based on research conducted by Jay Gordon (MIT). Below the fold is a summary of Gordon’s methodology: Continue reading →