AMC Stubs, the membership program for AMC Theatres, has surpassed 20 million households. According to the chain, more than 50 million moviegoers in the US are using Stubs. The three-tier program is made up of the $15-a-year Stubs Premiere; Stubs Insider, which is free; and Stubs A-List, its movie-ticket subscription platform, which starts at $19.95. […]