What is the fine-grained topic of the following text: The highly-serialized show has fallen heavily this season (currently down 45%), but had to endure a move from one of the network's best slots (Mondays at 10 after The Voice) to one of their worst (Sundays at 10 after World of Dance). Only return the topic.
Decline in viewership ratings of a serialized TV show due to time slot change.