Here’s the requirements for membership in the Academy of Motion Picture Arts and Sciences, as taken from the Wikipedia entry on the organization:
Membership in the Academy is by invitation only. Invitation comes from the Board of Governors. Membership eligibility may be achieved by earning a competitive Oscar nomination, or two existing members may sponsor a candidate from the same branch to which the candidate seeks admission.
The majority of members in the Academy, as you may expect, comes from nominations. Go ahead and look up the nominations, from the very first Oscars up to now, anywhere on the Oscars own website or by category on Wikipedia. Here’s one: Best Cinematography. Go ahead and look through the nominees. Tell me when you get to the female name. Oh wait, you won’t. From the Wikipedia page on this Cinematography award: “No woman has ever been nominated for an award on this category, this makes it the only category in the Academy Award’s history where no female contender has ever been nominated.” With the exception of the Best Actress and Best Supporting Actress Oscars, and the one for Best Costume Design, the overwhelming majority of all nominees have been men. For most of the Academy’s history, that’s meant white men.
The Academy currently has upwards of 94% white membership and 76% male membership. The problem of people of color not being nominated and female-centric movies like Carol being snubbed isn’t going away soon unless the Academy changes the membership rules, perhaps by opening membership up far beyond just nominees and invitations by other members, perhaps to all working union members. And the unions have their own problem that needs to be addressed: Women and people of color are woefully under-represented in the editing, directing, photography, and other film-making fields of pursuit. I don’t have the solution but I do know the problem isn’t going away any time soon because each year another crop of predominantly white, predominantly male nominees gets added to the membership rolls, self-perpetuating the very thing we’re trying to change.