A colleague of mine wrote a sentence of the following sort. I'd like to know if more likely to have died is used properly. The use of likely here does not seem to indicate uncertainty. How many of the respondents died should be verifiable by the researchers as a black-and-white matter. Also. from the way the sentence is written, it does not seem to be a general statement referring to drug takers in general. So why is "likely" used here at all?
Following up twenty years later, the team learned that among the original 5,500 interviewees, those who had said they took drugs in their teens were 25 percent more likely to have died. Many of them died of cancer.