How big is the neck tie industry in the United Kingdom? If I was to estimate the size of the neck tie industry in the United Kingdom, let's first assume that it's mainly men who wear neckties. So that's 50% of the population. So 50% of around 70 million is 35 million, so that's 35 million men. Of those 35 million men, let's assume that 70% are older, and already have enough neckties, don't work in an office, or are too young, so that leaves us with 30% of the male population. So 30% of 35 million is around 10 million people. And then let's assume that the average person buys one neck tie a year, at 20 pounds. So 20 pounds times 10 million is 200 million. So I'd estimate the size of the necktie industry at 200 million pounds. - This is a classic, "How do you think," question. The great thing is that there is unlikely to be a correct answer. The interviewer is just interested in how you think. Giving yourself assumptions, makes it clear how you've arrived at your answer. For example, 50% of the population are men. 70% are retired or don't work in offices, et cetera. The interviewer may put you on the spot though, by adding another assumption to see how you react. So for instance, they may say, "I can tell you, that your assumption of 70% are retired or don't wear ties, it's actually far too high. Give me another assumption." They aren't telling you that you've done something wrong. They just want to see how you react, and whether you can think on your feet. Perhaps you change your assumption quickly, or just think of something else. Don't be surprised though, if you feel you get this kind of question wrong. The interviewer is just trying to stretch your abilities.