The list was created by veteran entertainment journalist James Ulmer, who developed a 100-point method to quantify a star's value to a film production, in terms of getting a film financed and the cameras rolling. Bankability is determined for films in three different budgetary levels: $5 million or less (typically independent productions); $5 to $25 million; $25 million or over (studio films). A total score of up to 300 possible points is achieved by adding up the rankings for each budgetary level.
Ulmer calls his method "The Ulmer Scale," naturally, and the A-list is part of a larger guide called The Hot List that has become an industry-standard guide in Hollywood. Lesser-known actors inhabit the B+, B, and C lists, and there is even a dreaded "Bottom of the Heap".
The Ulmer Scale also takes into account an actor's history (box office successes vs. flops), versatility, professional demeanor, and his or her ability and willingness to travel and promote the film.
If an actor has 100 points on the Ulmer Scale for a given budget, that means that a movie on that budgetary level can have 100% of its financing guaranteed on that actor's participation alone. Very few stars have that much clout in the "$25 million or over" range, and the ones nearest to it occupy the A-list.
An even smaller number of stars (fewer than fifteen) occupy the A+ list, and these are stars with a solid 300 rating. These include the likes of Tom Cruise, Tom Hanks, Russell Crowe and Jim Carrey. After years at the top of the A-list, Julia Roberts became the first actress on the A+ list.
Ulmer has also developed a Hot List of directors.