Expert opinions are often based on economic models which use incredibly simplified assumptions and questionably appropriate mathematical techniques. At least this guy is willing to post his model for the world to pick apart.
As a direct criticism, the choice of the Normal distribution adds nothing to the model other than acting as a cover for the author's choice of point estimates. I believe you would get the same results independent of the distribution. Choosing a Normal distribution serves only to create an apparent range of results that are weighted towards the author's preferred choices of values.
Peer-reviewed economic models would have to justify their model assumptions in a more robust way, including empirical data where appropriate. I'm not an expert but I expect this is a good place to start:
http://www.journals.elsevier.com/economic-modelling/
All models use simplified assumptions and questionably appropriate techniques, I agree - that is practically the definition of 'model'. However, a useful model should justify those assumptions and techniques using current research-level knowledge, and/or show how the model applies successfully to reality.
I see this model to be as useful to economic discussion as saying "the world is flat, plus or minus 5 degrees". It ignores all current work in the field.
If you're expecting research-level detail in a blog post from someone who is admittedly not an economist, your expectations are too high. The post was meant to present a simple Monte Carlo simulation in Python using a current topic as its subject. He isn't writing a NYT Op-Ed citing his results as evidence that BJ > BI based on sophisticated modeling techniques.
