Penetration

The proportion of potential customers who have bought the category at all, as opposed to the share among those who have.

An Indian category at 28% household penetration has a different growth arithmetic from one at 85%. The first grows by bringing new users in, which is slow and depends on income; the second grows by frequency and price.

Confusing the two produces most bad forecasts in consumer analysis. A category near saturation cannot grow at the rate it did while penetrating.

Ask which stage the category is in before extrapolating anything.