Why the Mathematics of Finance are Crap

I will give you this (admittedly old) example from Global Economic Intersection, which explains in very simple terms, how much of finance is much closer to a confidence scheme that we would like to imagine:

"If Timmy brings 100 marbles to school and lends them to his classmates at 5% interest for the day, and the classmates diligently work to trade and earn and win enough marbles to pay their debts, how many marbles will Timmy collect at the end of the day?"

The banker will promise a 5% return, and my guess is that a lot of you thought the same thing.

Only it's not true.

Most of the pupils are of the linear thinking neoclassical persuasion steeped from the cradle in "banker arithmetic", so they sharpen their pencils and calculate that Timmy will receive 105 marbles in total principal + interest. "Profit drives the marble economy", Teacher correctly explains, "which is why the classmates were all so busily engaged working for marbles." And the pupils agreed it would be great fun participating in a marble economy where you could exercise your talents to get out more than you put in.

But little Warren had failed to cram his head into the neoclassical pencil sharpening box where you learn banker arithmetic and he exclaims, "But there ARE only 100 marbles, so unless Teacher adds marbles into the room, Timmy can only get back as many marbles as he put in. So the correct answer is Timmy will get back 100 marbles and some of his classmates will default on their debts and suffer a life of stupid unemployed poverty because Teacher says "We must live within our means." and she refuses to add the needed marbles even though she owns the marble factory that produces unlimited marbles at virtually no cost."

Yes, his is a metaphor for the Euro Zone, and the Austrian school ratf$#@s who make up the Bundesbank.

Read the rest.