probabilities

And Now, the Weather

© Can Stock Photo / ifeelstock

When you watch the news and the weather forecaster tells you there is an 80% chance of rain tomorrow, what exactly does that mean?

It might rain tomorrow, or it might not. It says rain is more likely than not. So if there is no rain after all, does that mean that the forecast was wrong?

Forecasting is often a fuzzy subject. No one can see the future with 100% certainty, so predictions are often spoken of in terms of probabilities. But we as humans are generally not good at thinking in terms of probability. An 80% chance is far from a sure thing, but when someone tells us something is 80% likely to happen, it can sometimes feel like one.

This is particularly true when it comes to trying to predict one-time events. If you flip a coin and it comes up tails, you can keep flipping it and see that it will still come up heads about half the time. If the weather forecast says there is an 80% chance of rain next Tuesday, there is only one next Tuesday. If Tuesday comes and goes without any rain, it sure feels like the forecaster blew it.

Economic and financial forecasting runs into the same problem. First, a forecast is only as good as its model. Economic projections may include assumptions that prove to be unfounded. But even a good forecast is limited to predicting a range of probabilities. If an analyst tells you they think there is an 80% chance that the market will go up this quarter, all they are really saying is that it might go up and it might go down. You probably did not need an analyst with a fancy model to tell you that.

We put little faith in short term market predictions. Even if they are accurate, you can probably not afford to bet the farm on them. We prefer to take a longer-term view. We cannot be sure how an investment will perform over the next month or next year, and do not believe in speculating on short term results. We feel much more comfortable in the trend over the long run.

Clients, if you have any thoughts or questions, please call or email us.


The opinions voiced in this material are for general information only and are not intended to provide specific advice or recommendations for any individual.

All investing involves risk including loss of principal. No strategy assures success or protects against loss.