The NFL continued to grow, eventually adopting some innovations of the AFL, including the two-point conversion. It has expanded several times to its current 32-team membership, and the Super Bowl has become a cultural phenomena across the United States. One of the most popular televised events annually in the United States, it has become a major source of advertising revenue for the television networks that have carried it and it serves as a means for advertisers to debut elaborate and expensive commercials for their products. The NFL has grown to become the most popular spectator sports league in the United States.