I recently graduated from Cal Poly San Luis Obispo, in Civil Engineering. I know that engineering is different from tech, but it's another white collar job.
Of the class of CEs, around 1/3 were women. CE is broken down to Structures, Geotech, Water, Transportation, and Construction Management is often done as well. Very few of the women went into Structures. It's the choice of the student on which way to go, and some are more difficult than others (Structures probably the most difficult). Women in the Structures program were on the order of 10%. Most of them seem to go into Transportation and Water. Similarly, the Hispanic students mostly went toward CM/General. I can't say about Blacks, there was only one in the class of ~120.
For whatever reason, it's primarily white and asian men who chose Structures. I work for a small company, it's overwhelmingly male and entirely white/asian (including mix of them).
From what I've seen, it isn't that underrepresented minorities and women are prohibited from going into Structural Engineering, it's that they choose not to. The women I have seen in it are quite capable, so I'm not sure why...