To continue the mostathon: when I said that most "licenses a default generalization," I meant to suggest that it has a kind of generic quality — you can't account for its use by assigning it a purely quantitative or numerical meaning (i.e., "more than half"). One way to make the point is to borrow Mark's method and look at examples where most would have been licensed but the writer chose instead to go with many. These are actually quite plentiful:
Among people who did seek out help for their depression, many (68.8 percent) saw or talked to a medical doctor or other health professional.
Many parents surveyed — 62 percent — say they've taken away their child's cell phone as punishment.
Once again, many employers (53 percent) are not yet sure which action they will take.
Why didn't these writers use most instead? It isn't always easy to say, but some of the examples are suggestive.
Let's say that many means "a significantly large number," whereas most denotes a group large enough to represent the default case — which will most often but not invariably be more than half (cf Mark's examples of most = < 50%). It often happens that the fact that such-and-such a property applies to the majority of instances isn't in itself significant — that is to say, it doesn't license any conclusion that wouldn't be licensed if the property applied only to a large plurality. In those cases many seems the more appropriate term:
Many independents — 55 percent — are extremely or somewhat likely to vote for a Republican Congressional candidate this year with the "specific intention of providing a check on Democratic control of Congress and the president.
Many employers, 42 percent, plan to extend dental plan coverage to adult children in order to match their medical plan requirements, and 32 percent plan to extend vision benefits to adult children. Once again, many employers (53 percent) are not yet sure which action they will take.
In the first example, I think it would be odd to use most (though "a majority" seems okay): the point is not that this is a characteristic or dominant property of the independents surveyed, but only that it holds of a significantly large number of them — the interest of the result would presumably be little different if the figure were 45 percent instead of 55 percent. In the second example, too, most would be odd (but "a majority" less so): the point is simply that a large number of employers are not sure what they're going to do, not that this uncertainty is a dominant characteristic of the group. In fact you sometimes find many used in place of most even when the proportion is very high, so long as what matters is the absolute number of people who have the relevant property rather than their dominance in the larger category:
Many Echo Boomers (88 percent) agree that they do not know as much as they should about retirement investing and the majority (71 percent) would like to receive more information and advice from their company on how to reach their retirement goals.
The following example gives a nice minimal pair:
In this sample of 397 homeless adults, 72.1 percent were male. The median age was 35. Most respondents (72 percent) had completed high school. Many (66.5 percent) were black.
What the writer wanted to suggest, I surmise, is that the large proportion of respondents who had finished high school allowed one to take that as characteristic of the group, whereas the fact that more than half were black didn't license a similar conclusion — the implication might have been more or less the same if only a third were black, provided that was a significantly large number. (This really is a minimal triplet: the writer could have used either most or many with the percentage of males in the survey, but that figure was presumably neither significant in its size nor characteristic of the sample of the whole.)
In this connection, by the way, I don't think Mark is right to say that the following example offers "striking evidence that most = >50% is alive and well in some quarters":
Many dancers (49 percent) were comfortable or very comfortable in revealing their occupation to others. Interestingly, most (52 percent) respondents viewed exotic dancing as a promiscuous activity.
All this shows, I think, is that the writer feels that the proportion who regard exotic dancing as promiscuous was sufficient to make that a notable feature of the entire group — if the writer had been impressed merely by the absolute number of dancers who held this view, s/he could have used many in both instances.
Qualifications: I'm not sure if "default generalization" is quite the right way to describe this. And it may very well be that the inferences associated with most can be generated by a judicious application of the Gricean maxim of quality to a purely quantitative meaning, though this account would also have to explain why most is sometimes infelicitous in contexts where "a majority" is fine.