Is this week a glimpse into the near future of what broadcast TV’s fast national ratings will look like? All week, HUT (households using television) levels have been on par or even slightly higher than last week (with the exception of Valentine’s Day.) And yet, there have been massive across-the-board ratings declines every night. If the total number of people sitting in front of  TVs has been roughly the same and they were not watching broadcast shows, what were they watching? Certainly not cable series, many of which also posted declines this week. I think a footnote in the HUT definition may hold the key to the puzzle. In addition to live viewing, it also accounts for people watching pre-recorded shows on playback.

The theory is that a blockbuster TV event like the high-rated Grammys on Sunday created a “tsunami effect,” with people catching up on previously recorded shows as well as possibly replaying the Grammys, instead of watching that night’s programs. That perpetuated for a few days, especially with Valentine’s Day in the mix when many people were out, creating an additional backlog of shows on their DVR. The theory is supported by measurements that registered a higher-than-usual level of playback viewing this week. It also could explain the biggest head-scratcher that was the Monday ratings, which featured the most extensive across-the-board ratings declines, including in the unflappable CBS comedy block, which had been heavily promoted during the Grammys the night before. (BTW, Nielsen’s explanation in response to queries from the networks about the lower Monday ratings was that it was Lincoln’s birthday. How many of you remembered that Monday was Lincoln’s birthday?!) Also in support of the playback theory, things began to go to normal last night in the 9 PM and 10 PM hours. There were still inexplicable net losses at 8 PM — CBS’ The Big Bang Theory did a 5.0/15 in 18-49, down 11% from last week, Fox’s American Idol (4.6/13) was down 12%, while NBC and ABC were on par with last week in the hour — Wipeout (1.5/4) was flat, while 30 Rock (1.4/4) and Parks And Recreation (1.7/5) were close to the demo delivery of an hourlong 30 Rock last week (1.6/4).

But at 9 PM, things began to stabilize. Yes, ABC’s Grey’s Anatomy (3.1/8) was down 23% to a season low and CBS’ Person Of Interest (2.9/7) and NBC’s The Office (2.2/6) and Up All Night (1.5/4) were down 12%. But last week, they aired against The Finder on Fox (2.3 in 18-49) vs. the second hour of American Idol (5.0) this week, so the total 18-49 rating in the hour remained approximately the same. Ditto for 10 PM, where CBS’ The Mentalist (2.8/7) was down 7% and a Grimm rerun (0.7) fetched half the rating a Voice encore did last Thursday, but ABC’s Private Practice (2.6/7) shot up 18% from last week with a Grey’s Anatomy cross-over. If the theory is correct, people should be all caught up on their DVR viewing by the end of the weekend and Live+Same Day ratings should return to normal next week, while Live+7 numbers for last week should spike. If not, Nielsen will have some serious explaining to do.