"Netflix is still the No. 1 subscription streaming service in the U.S., according to a new report from eMarketer, but rivals, including Amazon Prime Video and Hulu, are starting to cut into its market share. The analyst firm forecasts 182.5 million U.S. consumers will subscribe to over-the-top streaming services this year, or 53.3% of the population. Netflix is still the top choice here, with 158.8 million viewers in 2019, and it is continuing to grow. However, its share of the U.S. over-the-top subscription market will decline even as its total subscriber numbers climb, the report said."

what kind of market structure change could be occurring and why?