Is structural discrimination a core belief of feminism?

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Is structural discrimination a core belief of feminism? I find the claim that women are through all times and societies worse off than men (like in the question posted on on January 23, 2015; ) an assumption that is ideologically biased and needs further investigation. "Worse off" contains difference in preferences (having to go to war, economically being responsible for a family, being statistically more prone to a violent death). Doesn´t the problem lie more in being tied to a predefined role to which each sex is tied, each one with its pro and contra, with variation across times and societies? thank you!