The surprising success of equal-weighting schemes has an important practical implication: it is possible to develop useful algorithm without any prior statistical research. Simple equally weighted formulas based on existing statistics or on common sense are often very good predictor of significant outcome.

In a memorable example, Dawes showed that marital stability is well predicted by a formula:

Frequency of love making minus frequency of quarrels.

You don’t want your result to be a negative number.

Daniel Kahneman; Thinking, Fast and Slow; Page 226.