Look at the Mercer survey results on compensation in engineering (Canadian data). Salaries between men and women are within 5% for those at levels A to D (average 8 years of experience).
However, the longer one works in engineering, the wider the wage gap becomes between men and women. The largest discrepancies between the salaries of women and men occur in the most senior level positions.
By far, the widest gaps in compensation occurred in the highest level of responsibility (Level F). Women salaries were 10% lower. In monetary terms, this translates to about $15,500 less than the men in comparable positions.