[TeMPOraL]

I spent past 30 minutes skimming the first paper (available here[0]). Fine, so severity itself doesn't really work as a deterrent - with the caveat made by study, that it applies to "variation within the limits that are plausible in Western countries". I.e. changing the punishment of some crime from 2 years to 3 years does not create meaningful extra deterrence; changing it from 2 years to 25 years or capital punishment just might. I'd argue that changing the punishment from "a fine" to "prison sentence" may just do the trick too.

> This would make sense if humans were all rational actors who only took an action after performing the risk calculus of expected reward vs. potential punishment. But that's not how humans work

This is indeed how humans work sometimes. Not in the heat of the moment, but when coldly calculating how to make more money with less effort. Fraud is not a crime of passion, it's premeditated, evaluated in advance. More certainty of consequences, and perhaps the severity of them, may be what's needed to further reduce it.

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[0] - http://sci-hub.se/https://doi.org/10.1086/652230