I argue correlation/causation all the time -- but this is really a semantics argument on both our parts. The statement was "There's nothing in this graph that

I argue correlation/causation all the time -- but this is really a semantics argument on both our parts. The statement was "There's nothing in this graph that suggests market share is being taken away." I suppose the emphasis could be placed either on taken or away. No graph can show action ('taken') so as to demonstrate causation. That's why so many arguments are susceptible to "correlation/causation" trouble. As you suggest, there are any number of causes for the data given. To seek proof of causation from a single graph is a flawed venture. But if we look at whether market share was reduced ('away'), an observation may be made from a single graph. Not to say 'why' or 'how much', but the observation is still valid. If you sell 90 cars last year, and 110 cars this year -- and I sell 5 comparable cars last year and 50 comparable cars this year, I have "taken market share" from you in a generally accepted sense. Within the market space of two, I have more share of our market this year than the previous, even if your sales did not decrease. It doesn't matter how I did it (cause). It may not be true next year (correlation). It may not be universally true -- if there were 500 of this kind of car sold last year, and only 400 cars this year, your share of the total market increased. My conclusion before, and again: "the mix has steadily changed. If that's not market share loss, what is it?"