[dragonwriter]

> "[...] where all but about 80% of women end up changing their major [...]"

> In other words, 20% of women end up changing their major.

Or very nearly 80% [1]. Its generally just better to avoid "all but" in quantitative contexts; in qualitative contexts its clear, but in quantitative ones its clear-as-mud.

[1] http://www.merriam-webster.com/dictionary/all%20but

[calvinlough]

Ah, very interesting. I never even thought about it that way. So maybe the author wasn't trying to be misleading, but just chose their words poorly.

[jack-r-abbit]

I've never thought of "all but" to mean "very nearly". I've always thought of "all but" to mean "everything except". So in (probably) all the cases where "very nearly" works, so does "everything except". Unfortunately, the reverse is not true. I too thought her "all but about 80% switch" meant "everyone except about 80% switch" or in other words "about 20% switch". I thought it was weird to word it that way.