A brief piece about nothing in particular to celebrate the weekend and to help you negotiate your next salary increase. If anyone ever repeats this article to me, I shall vehemently deny that I wrote it. The reason: it deals more with magic than with engineering or the relationship between value and salary.A friend asked how much he should charge per hour for his time. He was compiling a proposal and admitted he had not set an hourly rate for himself for many years. I suggested either $137 and hour or $173 and hour. He chose, used the rate involving a 3 and a 7 and won. It may be mere coincidence—or just the way the human mind perceives the world—that a rock pile at its natural angle of repose has a factor of safety of unity at an inclination of 37 degrees. Let me know if your pile, as dumped, stands at a different angle. I will not believe you.

Once I was called on to set the out-side slope of a 100-meter high embankment. We had no computers to calculate the slope’s factor of safety. A wise old Scotsman who had been the chief geotechnical engineer on two large earth dams advised me over a bottle of Saki to set the slope at  1.73 horizontal to 1.0 vertical. I did and got not a single question about the stability of the embankment. The dam was built, the mine operated, and today you cannot find it with Google Earth so well reclaimed and blended with the environment it is. 

I do not know whence arises this tendency to accept as correct any number that includes 3 and  7. I would rather pay my divorce lawyer $375 and hour than $400 an hour. The latter is so smugly expensive. The former so reasonable and full of value. 

In theory, you should carefully select every number: gather the parameters, do the testing, run many computer codes, do all the calculations, develop a second sense of the correct number and then get drunk and do what your belly dictates.  Sometimes this is called Engineering Judgment, but it never hurts to include 3 and 7 in your answer (or in your salary increase request.) It always impresses and never gives rise to doubt about your calculations, judgment or worth.   

It may be that even numbers carry an air of certainty and roundness that raises the suspicions of reviewers and bosses. It may be that the human mind is programmed to question exactness, even numbers that sound too exact. After all, 3 and 7 sound as though you have done the calculations not just guessed and are really worth the increase. The approach does not work with 1 or 9; I do not know why. Maybe they are just too close to multiples of 10. 

So if you are in a quandary, need credibility and are sure of your judgement—but not of your computer—and want to know how much you are worth to your company, set the value (increase request) at 3, 7, 37, 73, 137, 173 or 375 and you will succeed. Even if you use this “advice” only to set your salary increase as 3, 7 or better still 37 percent.

And if you do not succeed, tell me, but do not berate me. Thanks for listening, and good luck with that salary increase.