“When the first attempts at systematic weather forecasting were made, one idea was to look back through the records for a day where the weather was much the same as the day when the forecast was being made. The assumption was that the weather on the following day would be the same as the weather on the following day in the historical past. But surprising events are always occurring to disrupt this sort of forecasting.” (from Len Fisher’s talk on the ABC’s Okham’s Razor, 11 May 2016.
We laugh now at the absurdity of these first weather forecasters. However, many in the stock market still analyse charts of past stock prices to predict future changes (this is a bit more complicated, perhaps, but it still seeks to find answers to the future from the past) At least, if you get it wrong with stock prices, you lose a bit of money but can try again tomorrow. But if you apply these ‘looking back’ ideas to future infrastructure investment decisions that will impact our communities for decades, that is a very different matter.
Thirty years ago when I became interested in infrastructure planning, it was common to take a rising trend and simply extrapolate it and although it often resulted in major oversupply, we still did it. And we are still doing it! We just use more complicated algorithms.
But if not extrapolation of the past, what techniques are available for anticipating a changing future?