I know just a few months ago I saw this excellent 50min or so long video that was a discussion panel between two ivy league professors (one male one female) on the exact topic of the wage gap and how it related value-wise to potential discrimination as a cause. It was definitely a very relevant discussion by two people who know way more about this topic than us; I'm trying to track it down.
That said here were a few of the nifty relevant points:
1) Both agreed that what was acting was a combination of some discrimination, some cultural influences and some biological tendencies. For part of this they looked at some studies that looked at cultures that had very different values than the typical European one, and found that, at least in part, women tended to seek out much of the same jobs, and tended to have a lower pay, despite the different culture and discrimination things.
2) In general (note, I'm not saying they said this applied to 100% of women! This was a very broad generality, and if I'm able to track down the discussion I'll be able to tell you exactly how broad) the studies looked at values and found that much more often men tend to be more interested in "object-driven" jobs, such as scientists, engineers, etc., while women tend to be much more interested in "people-driven" jobs such as nursing or jobs that interact with clients. Part of our culture, however, tends to value "object-driven" jobs such as engineering higher than many "people-drive" jobs, and thus places a higher wage on them. One notable exception in the other direction they brought up is the field of nursing, which is a "people-driven" job and in which case many of the wages for women were just as high as those in the engineering fields.
3) Nursing was brought up as a relevant point several times, in that it's a field that essentially functions as the opposite of a STEM field gender-wise, and pays almost as well. It was somewhat discussed if the fact that we had some 9 women to every 1 male in the nursing field meant that we were not putting enough effort into drawing in male nurses, and how that example related.
4) Both professors agreed that at this point we simply do not have enough data to actually be able to draw a line in how much of the wage gap is related to discrimination/cultural stereotypes and how much could be related to a larger amount of biological predispositions. They both agreed that at this point much of the data is showing that the dominoes could fall either way, and until we have more data the opinion largely comes down to the individual opinions of the person or professor; there simply isn't enough data out there yet to clarify exactly how much of the wage gap is being contributed by each source.
I'll continue looking for that video. For now I'd like to remind everyone here that I don't think there are any of us here who would be willing to say that there is no discrimination in the workplace period (be that in either direction). We're all at least somewhat on the same side, so please remember to stay civil to each other and try not to get too hung up on the little details, since we pretty much all agree that there is somewhat of a problem, the only question is exactly how big it is (which, as noted by the professors in the video I'm searching for, is something we really just don't have enough data to nail down yet).