Ways to think about market size

First, at one end of the scale, there are those people who are entering an existing, fairly mature market, with a superior product or price, expecting to take market share. You can get people to buy yours, but not to buy more than they did before, so the question is how much market share you can take with a better operating model. Hence, the CEO at the time, Hans Snook, went around saying that the UK would go to 150% penetration and most people thought he was mad (note that the Cellnet ad was made two years later).

Source: www.ben-evans.com