I run a salary survey for design professionals every year and started looking into the gender wage gap when I took on the role. The 'gap' has ranged from about 17% (during the strong construction and manufacturing periods) down to about 10% (during the depths of the recession), but, averages out to about a 12% difference.
However, as Nrkoon mentions, the position gap is one thing to point out. I get so irritated when I hear the 'women make 73 cents on the dollar' or whatever because it's comparing apples to oranges. If we want to decrease that big glossy number, we have to start breaking down the data and seeing where we can change perspective and educational initiatives.
And, tdt67, I would have liked to have seen the data as well for a number of reasons. But, I also understand that the original article was a summary of only a section of that survey. They've got other articles and likely reports that reflect the data within it. http://media.dice.com/report/2013-2012-dice-salary-survey/
In the salary survey I mentioned, I could not conclusively prove that there WAS a wage gap. When comparing the pay, men were higher on average, but, women worked fewer hours and had better benefits packages. Unfortunately, due to my small dataset, I couldn't get too granular in my comparisons.
If I just tried to find all of the architects who worked on commercial projects who had a four year degree and 5-10 years of experience... I'd sometimes find myself with no women at all or such a crazy small sample size that there's nothing statistically significant about any of it.
Of course, whether there's a 'problem' just because there are more women in Interior Design than Industrial Design or because there are more women in Facilities Engineering than there are in Programming is a whole different issue.