"used to verb" means past habitual actions or past state that are not true in the present any more. The first "used to" must be a past state, but what about the second "used to"? Does it mean a past intermittent habitual action or a past continuous state?
I thought action-verbs are for intermittent habitual actions while state-verbs are for past continuous state, but with this example, there seems to be no barrier.
ex)Smoking used to be very popular in the US until its dangerous effects were discovered. A lot of studies were done and the trend has been changing. More than 40% of the population used to smoke, now less than 25% does.
Is it really likely that 40% of the population smoked non-stop, 24 hours a day? When analysing the meaning of sentences, common sense is usually more helpful than abstract grammar.