Graham, I agree you need to be careful about how you use the data, however to label the information as bollocks is not fair, how it is used might be but you can't blame the facts for that. I've looked at my subward and agree that if you use monthly data the standard error is likely to be too high to give you a meaningful trend so its better to look at annual data where the error will be lower as the population (of data points) increases. The popular view that statistics is a load of rubbish is not true, generally its how you use it, so I would say use it with care and you'll be fine.