Engineers’ love of technology often gets in the way of their being useful. Consider Post-it Notes or, better yet, plain paper notepads. These probably seemed like trivial ideas, but they turned out to be terribly useful. Why? Because the marvel that is the human brain has a horrible short-term memory, which means that dumb-as-dirt memory aids can make people substantially smarter.

Given a finite state space and common priors, common knowledge of the identity of an agent with the minimal (or maximal) expectation of a random variable implies ‘consensus’, i.e., common knowledge of common expectations. This ‘extremist’ statistic induces consensus when repeatedly announced, and yet, with n agents, requires at most log2 n bits to broadcast.