“I am creating a new bird-chirping, angel-singing, cloud-parting, paradigm-shifting product, so I cannot measure the market size, and I cannot forecast anything now”. Wrong! this is not true.
Market also follows the axiom of ‘First Law of Thermodynamic’ : E=MC2
Markets can neither be destroyed nor created. It can only be captured from one product to another. Without taking it word-to-word, or using exceptions, let us examine how we could determine market for new product?
A new product can capture a portion of existing market in the same competitive space, and also can capture a whole new market segment who may not have been using competitive product. For instance, think of iPad capturing some of PC market or automation facing challenges from cheap manual labor.
So, it may not be true that you don’t have numbers for the cool new product/ service that you are creating or working on. You always have the numbers as per this law.