Or maybe the data is flawed and doesn't actually account for all the different variables. Maybe women have more agreeable personalities and therefore are not as good at negotiating salary.

The article you linked to does imply a certain bias, but not getting call backs is much different than making less money. Did she submit both resumes to the exact same employers? If not then there's nothing scientific about it. As a male who recently had to search for a job, I had weeks where I'd get no callbacks, and weeks where nearly every company I applied to got in touch for a phone screen.

Even if the study was completely scientific and 100% accurate, it doesn't prove that there's a wage gap - i.e. two people doing the same job but the woman being paid less. The only thing this demonstrates is a biased perception towards certain people being qualified for certain jobs.

I'm willing to bet a male applying for teaching or nursing careers would experience the same bias.

I'm willing to bet you'd get the same results submitting a resume of someone who finished college in the 70s vs someone who graduated in the 2010s.

Long story short, plenty of biases exist, but to say employers are unfairly biased against women 100% of the time...I just don't think that's the case.