The book is closed on Rio. And, like all but a few of the nights of the 2016 Summer Olympics, ratings for the closing ceremony were down quite a bit from 2012's London Games.

Per overnight ratings from Nielsen Media, NBC's primetime coverage of the Rio wrap-up averaged a 11.7 rating among households between 8 and 10:30 p.m. ET — with that preliminary number down 31 percent from that of the London Olympics. Early audience statistics, per Nielsen's Fast Affiliate scores, paint a more depressing drop from 2012. The average 16.9 million viewers is roughly a 45 percent fall from London.

It's not surprising that the Closing Ceremony's ratings would be down from those of the London finale — 31.0 million viewers and a 17.0 rating among households — four years ago. Though many nights of the Rio competition closely trailed comparable outings in London, the Opening Ceremony was off by as wide a margin as well.

On Sunday, NBC Sports announced that the 15 nights of primetime Olympic coverage averaged 27.5 million viewers — per its Total Audience Delivery statistic. That combination of simultaneous broadcast, cable and live-streaming reach still falls quite short of London. The 2012 Olympics averaged 30.3 million viewers for competition — with an even higher overall average. Bolstered by especially strong opening and closing ceremonies, the London Games averaged 31.1 million viewers in primetime and a 17.5 household rating.

As of Monday morning, the Rio primetime average is 24.3 million viewers on NBC alone. Even with the Total Audience lifts, and the slight pop from Sunday's ender, it is clear that Rio will fall considerably shy of London's showing. Still, much off that loss falls on the Opening and Closing Ceremonies. The actual competition, when stacked against London, is less than 3 million viewers shy and narrowly bests Beijing in 2008.

A week into the Summer Games, NBC Sports topper Mark Lazarus told reporters that the company was still selling advertising space and would be able to make good on its ratings promises. But the addition of cable and streaming, which swelled past 2 billion minutes of live viewing, does not fully compensate for audience dips. And Rio will not be meeting the average 17.5 household rating that the network is said to have promised advertisers.

The Olympic lead-in didn't do much for The Voice. A special preview of the coming season, which adds high-profile coaches Miley Cyrus and Alicia Keys, averaged a 2.7 rating among adults 18-49 and 10.4 million viewers. Both great numbers, for sure, but nothing atypical for broadcast's dominant reality series.

ABC's game-show block of Celebrity Family Feud (1.1 adults), $100,000 Pyramid (1.0 adults) and Match Game (0.9 adults) was improved compared with their last original Sunday outings. CBS' Big Brother held even with a 1.8 rating among adults 18-49, while BrainDead only pulled a 0.3 in the key demo.