[ajb]

It is difficult to get a man to understand something, when his salary depends on his not understanding it.

[renewiltord]

It is also difficult to get a man to understand something when you are not familiar enough with the subject. I suspect that is the more common failure mode.

[SantalBlush]

This HN cliché notwithstanding, economists actually do understand a lot more about the study of economics.

[imtringued]

It's just the general strawman. People only see economists when they fail so they think all economists fail even though it is only a subset.