iSuppli is on to something, and it’s about time.

The research firm today distributed its estimates for the smartphone market in 2009. But instead of forecasting a single number, the company provided a range based on the best- (new options compel new purchases) and worst-case (customers sit on their wallets) scenarios.

This is a much wiser, useful way to approach forecasting. Whereas some may call it a copout — by providing a range, iSuppli gives itself a greater chance of being “right” — I see it as a long overdue move into what is standard practice elsewhere. Indeed, providing a range is a method many researchers in other fields use to describe what might actually happen.

The next step would be to offer probabilities for the different scenarios; in other words, 50% of the time, sales will be up by X%; 75% of the time, sales will be up by Y%, and so on. But I’ll settle for other research firms picking up on what iSuppli has started. Kudos!