But the back testing is useless because you can just have a lot of models and cherry pick all those models which happen to match historical data. Then each year some of those models are proven wrong and the attention shifts towards models which happened to get it right... And new models are invented constantly. If you have enough models and companies working on them, you will always find a few which just happen to have guessed all the numbers correctly. It's like lottery. Out of millions of people, some people will get all the numbers right.