In the past, it was easier for men to get promoted than women.
「有利」を訳さなくていいです。
It was X to do... の構文は「（すること）がしやすい・しにくい」を表します。
昔は in the past
前に言った構文を入れて：
it was easier to get promoted
「男の方は出世しやすかった」は it was easier for men to get promoted になり
「女より」を加えると promoted のあとに than women をつけます。
「なぜか」という文章で続けたら
In the past, it was easier for men to get promoted than women because women had to take maternity leave when they had children.
「昔は男の方が出世しやすく有利だった。なぜかというと女性は子供をできたら産休をとるはずだったから。」
という英文になります。
In the past, men didn't have maternity leave and so were less risky for employers to promote.
Since men do not get maternity leave, they are a more known quantity at work.
As opposed to women, who might leave work at anytime to raise kids, men are less prone to drastic changes in their lives. So they get all the promotions
僕の妻も今は産休を取っていますので、心配になります。
・「In the past,」昔は「men didn't have maternity leave」男は産休なかったから「 and so were less risky for employers to promote.」雇い主の立場から見ると雇用のリスクなかった／｛リスクが少なくて｝出世しやすい
・「Since men do not get maternity leave,」男は産休がありません。従って「 they are a more known quantity at work.」男は状況があまり変わりません。
・「As opposed to women,」女の人と違って「 who might leave work at anytime to raise kids,」突然に職場を出て育児をしたりする「 men are less prone to drastic changes in their lives. 」男の生活は安定していて勤務状況はそんなに変わらない「So they get all the promotions」従って出世されるのは男ばかりです
アメリカ合衆国 
オーストラリア 
