August 1996 by Ian Stewart

Reproduced with permission of the author

The April column "How Fair Is Monopoly?" generated the largest mailbag ever. Most readers pointed out that the analysis ignored many features of the real game, notably the "Go to Jail" square but also the Community Chest and Chance cards. Some readers assumed that I didn't know the rules of the game, whereas others deduced (correctly) that I had made some simplifying assumptions but did not make them explicit. One reader wondered if the article was an April Fools' spoof: no, not an intentional one!

A few readers provided the missing analysis of the realistic game. I wish to acknowledge in particular Stephen Abbott of Northfield, Minn.; William J. Butler, Jr., of Portsmouth, R.I.; Thomas H. Friddell of Maple Valley, Wash.; Earl A. Paddon of Maryland Heights, Mo.; and David Weiblen of Reston, Va. Together, they have taught me a great deal - so much so that I intend to report their results, and any others that come to my attention, in a full column.

In reality, the "Go to Jail" square definitely produces a skewed probability distribution. The jail square itself is the most frequently visited, with a probability of 5.89 percent as compared with the "equidistributed" value of 2.5 percent (or 2.44 percent if 'Just Visiting" and "Jail" are distinguished, which seems sensible). The next most likely square to be landed on is Illinois Avenue, with a probability of 3.18 percent. The square least often visited is the third "Chance" square around from "Go," probability of 0.871 percentapart from "Go to Jail," which is not actually visited at all, because you're off to the pokey.