Television heads into its biggest week with the hangover from a 100-day writers strike persisting. Viewership is down, although it’s hard to tell how much the strike is to blame. This week’s “upfront” presentations by broadcasters outlining their fall schedules, which annually precede a multi-billion-dollar ad-buying binge, promise to be very different than before.

ABC, CBS, Fox, and NBC had nearly 9% fewer viewers in April and May so far than during the same period a year ago, according to Nielsen Media Research.

Yet viewership declines are sadly typical for the big networks. Take the same period a year earlier, and the drop was more than 5% over 2006. People didn’t watch less TV while the strike was on; they just watched cable more, said Steve Sternberg, an analyst for Magna Global.

Shows with ongoing stories seemed to lose the most momentum from the strike; ABC’s “Grey’s Anatomy” on May 1 had its smallest audience since moving to Thursday night. Decisions by NBC to keep “Heroes” for next fall and by Fox to delay “24” until next season may prove prescient, unless people forget about the characters altogether.

Comedies were hurt least by the strike. CBS was so buoyed by the performance of its Monday-night comedies that the network is considering adding comedies on another night.

CBS’s rack of procedural dramas had done relatively well, at least until a week ago: “CSI: Crime Scene Investigation” had its second-least-watched episode for a Thursday original, and “CSI: Miami” hit a series low for an original.