Tyler opposes even semi-formal clothes:

Marginal Revolution: Bargain in your pajamas, or blog in suit and tie: [If] dressing up actually... make[s] people more productive... would not at least a few of us blog in suit and tie?

In short, I don't have a theory of corporate dress that fits the major data points.  My best guess is that signaling by dress is often an efficient means of sorting -- Jamie Cutthroat really does want the promotion more than I do -- and thus the employer does not want to ban it...

Well, Tyler, I hate to bring this up, but right now...

Admittedly, the jacket is mostly to keep warm--see David Friedman, "A Paradox of Rational Heating". The tie--well, it (a) saves you from having to carry around a napkin, and (b) expresses one's solidarity with the Croatian irregulars who are defending Christian Europe against the Ottoman Turkish Janissary Menace.