(SOURCE). In 2013, when looking at an equivilent full time, full year worker comparison women made 91% of what a man made (SOURCE).
However, as I previously suggested....as is often the problem people look at a single point of data and (thanks Kush, you introduced the word into play) due to confirmation bias just assume it MUST be because of their view on it.
There's a definite gap between pay of male and female nurses; however, that fact alone is of litlte use without an understanding of WHY there's a gap, and how much does each variable factor into the ultimate number. For example, one link points out that despite male nurses being a small percentage of the TOTAL population (6% in 2010, 10% in 2013), they have a larger representation within nursing specialities that generally command a higher price point. For example, in 2010 49% of the anestic nurses in the country were male, and that position tends to make a larger amount than a normal nurse working the floor of a hospital...but both would be counted as a "nurse". Additionally, education impacts pay, and as of 2010 it appeared more men were entering into higher education levels for nursing then women. WHAT kind of nurse, and education level, are just two possible factors in play here that would need to be examined.
Is a systematic bias towards men by those in power a possable factor? Absolutely, but the question is generally "how much". The question is also comes down into what is the cause of some of the other factors and is it something that needs, or can, be "fixed" via government action.
I've not seen anyone really disagreeing that there is a wage gap, but simply suggesting that there's hardly one universally absolute method in which to read it and that each method of how to determine it can have its flaws and issues depending on WHAT you're actually looking ot measure. And that while it may exist, the extent that it exists in a way that needs active government intervention to be able to fix is in dispute.