NBC’s Olympic gains over 2004 are shrinking, but the network is still drawing strong ratings for Beijing in week two, traditionally the lower-rated portion of the Games.

On Monday, the network averaged 26.4 million total viewers in primetime, up 2 percent from the comparable night in Athens four years ago, which averaged 25.9 million.

Among households the network was actually down a smidge from Athens, averaging a 15.8 rating and 26 share to the latter’s 16.4/27, according to Nielsen.

But for the 11-day Olympics thus far, NBC’s primetime remains way ahead of Athens in both total viewers and households. The network is averaging 29.6 million total viewers, 13 percent better than Athens’ 26.2 million. In households, the network is drawing a 17.2/30, 9 percent better than 2004’s 15.8/28.

NBC remains on track for the best non-U.S. Olympics since Barcelona 1992 averaged 18.4/35.

Still, the network’s momentum has clearly cooled a bit after the huge numbers for the opening week, which featured Michael Phelps’ eight gold medal run and the bulk of the gymnastics competition.

That’s not surprising. Nearly every Summer Games sees ratings dip from the first to the second week because the second-week events tend to be less popular.

The second week has slipped an average 12.5 percent the past four Games, dating back to Barcelona, according to an analysis by SportsBusiness Journal.

The smallest dropoff, 9 percent, came in 1996, when the U.S. hosted the Olympics in Atlanta. U.S. Games tend to see higher ratings generally.

The past two Olympics have fallen an average 12 percent in their second weeks, and that’s about where NBC stands right now. Monday’s viewership was off 11 percent from the previous week, when Phelps captured his third and fourth gold medals.

If ratings stay on a similar trajectory, NBC will still finish well ahead of Athens as well as Sydney 2000, the lowest-rated primetime Olympics ever.

And the network remains on pace to make its ratings guaranteed to advertisers, a 14.5. In fact, yesterday NBC said it had sold another chunk of inventory that had been set aside for makegoods.

The network has sold $25 million in ads since the Games began, including $15 million in the past week. That’s in addition to the $1 billion sold before the Games began.

More than 100 companies have advertised during these Olympics, and the network says interest has been particularly strong in movie, retail, packaged goods and pharmaceutical categories.

Meanwhile, 200 million cumulative viewers have now tuned into some part of these Games on broadcast or cable, putting Beijing just 3 million behind Athens with six days to go. NBC has predicted that Beijing will outpace Atlanta’s 209 million viewers to become the most-watched Olympics in history.