By Brian Stelter, CNN Business

(CNN) -- Preliminary ratings for Sunday night's Super Bowl 53 show a 5% decline from last year's game.

With almost everyone except Patriots fans calling the low-scoring game a snooze, it's a wonder that the ratings weren't even lower.

All told, when the final Nielsen numbers come in later on Monday, the game will likely come in a little under 100 million viewers.

The overnight household rating was 44.9, meaning that about 45 percent of all the households in America were tuned in to the game.

Last year the equivalent household rating was 47.4. The finalized total average was 103.4 million viewers.

The numbers come with a few caveats. First, the overnight ratings only measure viewership at home on TV sets. Bars, restaurants and other public viewing locations aren't counted in the total.

Second, streaming video viewership is measured differently, so the household rating doesn't count anyone who watched on the web.

And third, the ratings are an average of the per-minute viewership of all four quarters. Super Bowl viewership sometimes peaks around halftime and in the fourth quarter.

Despite the paucity of touchdowns, most households kept watching until the very end on Sunday night. The preliminary ratings showed viewership peaking in the 9:30 p.m. half hour, when CBS had a 47.3 rating.

Nothing else on American television even comes close to matching the scale of the Super Bowl.

But the ratings for the big game have been slipping for several years despite overall population growth. Even the Super Bowl isn't completely immune to the fragmentation of the TV business.

The last time CBS televised the Super Bowl, in 2016, the game averaged a 49.0 household rating.

Many factors affect football viewership -- even the weather in various markets across the country. Relative interest in the two teams is a big factor.

Sunday's relatively soft ratings -- compared with recent Super Bowls -- stand in contrast to a strong season overall for NFL viewership.

On average, NFL games were up 5% percent compared with the 2017 season.

Experts said a jump in offense -- high scoring and hotly contested games -- led to a jump in ratings.

Sunday's Super Bowl may be further proof of that thesis.

"Fans who were hoping to tune into a high-scoring Super Bowl were treated to the exact opposite, a defensive slugfest spurred by defensive masterminds on both sides," Yahoo senior NFL writer Terez Paylor wrote Monday morning.

It was the lowest-scoring Super Bowl in history. The Wall Street Journal's Jason Gay called it a "snoozer bowl for the ages."

Most viewers still stayed up and watched -- but it's no wonder why viewership was off from past years.