>This myth needs to die.
Let me spell it out in an example. Sports. Horse racing or basketball. You have a team of highly skilled players with a bunch of information quantized, including height, weight, score statistics, rebound statistics, biography... etc. And these guys are in a game with a very very controlled set of rules under exactly the same time pressure and everyone still fails to predict the outcome.
In software you have a product. The product is usually not concretely defined and you have a complex code base and you can never be 100% sure exactly how the new product will integrate with that code base... you're also not 100% sure how the code will be put together to define the product. Additionally are you 100% familiar with the stack? Do you know every possible primitive of psql or ruby or python or C++ that you could be using to create your project because I pretty much guarantee you every basketball player more or less knows every possible move and rule of a basketball game.
You're also working with a team that includes people that you have much less information on than normal. You worked with a guy for what at most two years does that give you accurate statistical information to the degree of say a basketball player? Also there's bound to be people you're less familiar with working on the project as well. Are you interacting with other teams as well? Does the outcome of your project hinge on the completion of a feature by an entire team outside of your own?
People can be experts on horse races or sports. Even then they can't predict things accurately. If you were to start making bets on software development dates of completion. You will also massively fail because not only are there more variables in a software project... but you have much less information.
Chaos is a phenomenon that happens to systems we have close to perfect information for. We find that if we have the perfect information of all the particles in a weather system except for say one particle. We find that information about that missing particle will make our mathematical calculation wildly inaccurate.
For software we don't even have anything close to perfect information in a system with multitudes of variables. Chaos will throw any prediction off.
>but most can predict how long things will take within a factor of 3x or so and it will be within that margin most of the time, a person who could do that for hurricanes or earthquakes would be the greatest genius in history.
3x of what. 3x can be big or small depending on x. So if I predict a project will take one year I can be off by 3 years under your logic. If I predict a month, than I can be off by 3 months. If I predict a week, 3 weeks. 3x is pretty horrible if you ask me, it's easy to make guesses within these parameters.
I predict that both a hurricane and an earthquake will happen in a century. I'll only be off by 3x or 3 centuries. Actually I can do better than that. I'm 100% sure multiple earthquakes and multiple hurricanes will happen in the next century and I am 100% sure that I will by 0x off let alone 3x.... Look I'm the greatest genius in history.
3x is not a reasonable margin of error.