Models

This is my first ever handwritten post. Wrote this using a Natraj 621 pencil in a notebook while involved in an otherwise painful activity for which I thankfully didn’t have to pay much attention to. I’m now typing it out verbatim from what I’d written. There might be inaccuracies because I have a lousy handwriting. I begin

People like models. People like models because it gives them a feeling of being in control. When you observe a completely random phenomenon, financial or otherwise, it causes a feeling of unease. You feel uncomfortable that there is something that is beyond the realm of your understanding, which is inherently uncontrollable. And so, in order to get a better handle of what is happening, you resort to a model.

The basic feature of models is that they need not be exact. They need not be precise. They are basically a broad representation of what is actually happening, in a form that is easily understood. As I explained above, the objective is to describe and understand something that we weren’t able to fundamentally comprehend.

All this is okay but the problem starts when we ignore the assumptions that were made while building the model, and instead treat the model as completely representative of the phenomenon it is supposed to represent. While this may allow us to build on these models using easily tractable and precise mathematics, what this leads to is that a lot of the information that went into the initial formulation is lost.

Mathematicians are known for their affinity towards precision and rigour. They like to have things precisely defined, and measurable. You are likely to find them going into a tizzy when faced with something “grey”, or something not precisely measurable. Faced with a problem, the first thing the mathematician will want to do is to define it precisely, and eliminate as much of the greyness as possible. What they ideally like is a model.

From the point of view of the mathematician, with his fondness for precision, it makes complete sense to assume that the model is precise and complete. This allows them to bringing all their beautiful math without dealing with ugly “greyness”. Actual phenomena are now irrelevant.The model reigns supreme.

Now you can imagine what happens when you put a bunch of mathematically minded people on this kind of a problem. And maybe even create an organization full of them. I guess it is not hard to guess what happens here – with a bunch of similar thinking people, their thinking becomes the orthodoxy. Their thinking becomes fact. Models reign supreme. The actual phenomenon becomes a four-letter word. And this kind of thinking gets propagated.

Soon the people fail to  see beyond the models. They refuse to accept that the phenomenon cannot obey their models. The model, they think, should drive the phenomenon, rather than the other way around. The tails wagging the dog, basically.

I’m not going into the specifics here, but this might give you an idea as to why the financial crisis happened. This might give you an insight into why obvious mistakes were made, even when the incentives were loaded in favour of the bankers getting it right. This might give you an insight as to why internal models in Moody’s even assumed that housing prices can never decrease.

I think there is a lot more that can be explained due to this love for models and ignorance of phenomena. I’ll leave them as an exercise to the reader.

Apart from commenting about the content of this post, I also want your feedback on how I write when I write with pencil-on-paper, rather than on a computer.

 


Moron Astrology

So this morning I was discussing my yesterday’s post on astrology and vector length with good friend and esteemed colleague Baada. Some interesting fundaes came out of it. Since Baada has given up blogging (and he’s newly married now so can’t expect him to blog) I’m presenting the stuff here.

So basically we believe that astrology started off as some kind of multinomial regression. Some of ancestors observed some people, and tried to predict their behaviour based on the position of their stars at the time of their birth. Maybe it started off as some arbit project. Maybe if blogs existed then, we could say that it started off as a funda session leading up to a blog post.

So a bunch of people a few millenia ago started off on this random project to predict behaviour based on position of stars at the time of people’s birth. They used a set of their friends as the calibration data, and used them to fix the parameters. Then they found a bunch of acquaintances who then became the test data. I’m sure that these guys managed to predict behaviour pretty well based on the stars – else the concept wouldn’t have caught on.

Actually it could have gone two ways – either it fit an extraordinary proportion of people in which case it would be successful; or it didn’t fit a large enough proportion of people in which case it would have died out. Our hunch is that there must have been several models of astrology, and that natural selection and success rates picked out one as the winner – none of the other models would have survived since they failed to predict as well on the initial data set.

So Indian astrology as we know it started off as a multinomial regression model and was the winner in a tournament of several such models, and has continued to flourish to this day. Some problem we find with the concept:

  • correlation-causation: what the initial multinomial regression found is that certain patterns in the position of stars at the time of one’s birth is heavily correlated with one’s behaviour. The mistake that the modelers and their patrons made was the common one of associating correlation with causation. They assumed that the position of stars at one’s birth CAUSED one’s behaviour. They probably didn’t do much of a rigorous analysis to test this out
  • re-calibration: another problem with the model is that it hasn’t been continuously recalibrated. We continue to use the same parameters as we did several millenia ago. Despite copious quantities of new data points being available, no one has bothered to re-calibrate the model. Times have changed and people have changed but the model hasn’t kept up with either. Now, I think the original information of the model has been lost so no one can recalibrate even if he/she chooses to

Coming back to my earlier post, one can also say that Western astrology is weaker than Indian astrology since the former uses a one-factor regression as against the multinomial regression used by the latter; hence the former is much weaker at predicting.