You can't? And you call yourself a Marketer???
Granted, market modeling was never the traditional purview of marketers, but seeing how Markets have evolved, gotten so much more competitive and so much more saturated, I don't know how you can pass up a chance to be smarter about the way your organization goes to market.
Wouldn't it be useful to know that if you altered the price point on your product or were able to modify its deployment time (or any other attribute of your offer) what the effect on your market share would be?
There's a whole mess of techniques to derive these predictive market models. Just take some of these with a grain of salt. Not all ways of predicting market behavior actually predict! Many chomp only on historical data so they predict "backwards" not forwards.
Seriously though, the ability to predict how your market will behave in the face of a change in strategy or offer execution is essential to being a smart CMO. Don't just be about the brand. Granted the brand is important but integrating marketing science into your GTM strategy will drive the brand (and of course Demand) to new heights.
You've got to be looking to pull every single competitive lever you can these days.. heck not just these days, all days. If you want to learn how to predict how you're market will behave, let me know and I will hook you up!