In the 1920s, what film studio was not included into the "Big Five" majors list?

A major film studio is a production and distribution company that releases a substantial number of films annually and consistently commands a significant share of box office revenue in a given market. In the American and international markets, the major film studios are commonly regarded as the five diversified media conglomerates whose various film production and distribution subsidiaries collectively command approximately 80–85% of U.S. box office revenue.

By the mid-1920s, the evolution of a handful of American production companies into wealthy motion picture industry conglomerates that owned their own studios, distribution divisions, and theaters, and contracted with performers and other filmmaking personnel, led to the sometimes confusing equation of "studio" with "production company" in industry slang. Five large companies: RKO Radio Pictures, 20th Century Studios, Paramount Pictures, Warner Bros., and Metro-Goldwyn-Mayer came to be known as the "Big Five" in trade publications such as Variety, and their management structures and practices collectively came to be known as the "studio system".

Walt Disney Productions was an independent production company during the Golden Age, then became a mini-major in the 1950s, and then became a major in the mid-1980s.

Today, the Big Five majors – Walt Disney Pictures, Warner Bros., Universal Pictures, Columbia Pictures, and Paramount Pictures.