What BeCoMe does

BeCoMe turns a panel's disagreement into one number you can defend, and tells you how much the disagreement cost.

The problem it solves

Ask thirteen experts how much arable land a country should convert to flood plains and you get thirteen answers, most of them ranges rather than single figures. On one Czech panel the hydrologists recommended converting 37 to 50 percent. The land owners, whose fields those would be, said 0 to 4. Both groups had reasons.

The usual move is to average everything, and it fails quietly. The plain average of that panel is about 20 percent: far too little for the hydrologists, ruinous for the farmers, and not one of the thirteen would defend it. It is also fragile. Add one more strong opinion at either end and the answer moves again.

Averaging also throws away the ranges. An expert who says "sixty, could be forty to eighty" and one who says "sixty, give or take two" have told you different things, and a mean of single numbers cannot hear the difference.

How it answers

Each expert gives three numbers rather than one: the lowest value they would accept, the value they consider most likely, and the highest. That is a fuzzy triangular number, and it lets someone say "around forty, but I could live with thirty-seven" without claiming a precision they do not have.

The method then computes two things the panel already implies. The average shows where the opinions sit in aggregate. The median shows where the middle of the panel sits, and it barely moves when one person takes an extreme position. BeCoMe takes the midpoint of the two, and reports the distance between them as a separate number.

That second number is the part most methods leave out. It says how far apart the panel was, so a compromise from a divided room cannot be quoted as if it came from a unanimous one.

When it fits

It fits when several people who know something must produce one figure, and when their uncertainty is real rather than a formality. Budget allocation across departments. How much of a policy to adopt. Any question where "about forty, but it depends" is a more honest answer than "forty".

It fits badly when there is a right answer someone could look up, when one person's judgment should win outright, or when the question is a choice between options rather than a quantity. For agreement questions it has a mode of its own, described in running a decision.

Where it comes from

The method was published in 2021 by researchers at the Czech University of Life Sciences Prague:

Vrana, I., Tyrychtr, J., & Pelikán, M. (2021). BeCoMe: Easy-to-implement optimized method for best-compromise group decision making: Flood-prevention and COVID-19 case studies. Environmental Modelling & Software, 136, 104953. https://doi.org/10.1016/j.envsoft.2020.104953

This is an independent implementation of that paper wrapped in a web application, so a panel can run it without writing code. The method description gives the mathematics in full, with worked formulas.

Ready to try it? Getting started takes about ten minutes, and your account arrives with the flood panel above already loaded.