How much more does a male construction worker earn then a female?

Generally the pay gap between males and females doing the same job is about 25% - lightly higher as the jobs become more manual and slightly lower as the jobs require more education.
In addition the jobs offered to women are not as highly ranked as those gven to men (men more often rech supervisor jobs) so the pay is again slanted towards men.
As far as the why, is is an inherent cultural bias. Legislationhas been brought in in many jurisdictions for equal pay for equal work. This has been not entirely successfulas job descriptions and evaluations can be slanted to produce desired biases and maintain the status quo.
The usual arguemnts are - men are naturaly btter than women (stronger, more mechanically inclined, heartier, etc.), men are the breadwinners, a woman's place is in the home, The Bible (Qur'an, out culture) says woment are subservient, it isn't natural for women to be in this line of work. ANone of these arguements are based in rational thought.