With its ratings surge, ABC is picking up the coveted upscale viewers that NBC has been crowing about for years-and winning new advertiser clients along the way.

So far this season ABC leads all four major networks in ratings among viewers in households earning more than $100,000 in both the 18 to 49 and 25 to 54 age brackets, a category NBC led a year ago at this time.

Because of its uptick in upscale viewers, ABC has been able to add ad revenues in the automotive, financial services and wireless communications categories, according to Geri Wang, senior VP of prime sales for the network. ABC is seeing more money from “anybody with a new technology aspect to their business that cares absolutely who the early adopters are. [It is upscale viewers who have] the discretionary income [and] who can make that next purchase,” she said.

But NBC’s shows continue to attract a percentage of upscale viewers disproportionate to its ratings, and by most accounts the Peacock Network leads its rivals, including ABC, with the highest concentration of $100,000-plus consumers.

The category is key for advertisers, especially those with big-ticket products who want to reach viewers with disposable income.

“NBC is still extremely upscale,” said Steve Sternberg, executive VP and director of audience analysis for Magna Global. “It’s not that they’re really getting hurt by this, it’s just that they’re no longer the only one that could hang their hats and say they’re upscale. Now ABC can do that also. It really helps ABC a lot more than it hurts NBC. It’s another sign of how they’re growing and how well they’re performing.”

ABC’s average ratings among viewers 18 to 49 with $100,000-plus incomes have risen to a 4.9 so far this season (through Oct. 23), up from 4.2 a year ago. NBC’s average ratings in the category dropped to a 4.3 from a 4.6.

But networks and ad buyers also look at an index that shows what proportion of a network or show’s viewership is above the $100,000 market, and NBC is No. 1 by that measure. NBC’s index grew to 125 from 116 last season, while ABC’s grew to 113 from 104.

NBC also had the six top-indexing shows, led by “The West Wing.” “NBC prime continues to have the highest upscale index of any broadcast network-in all key demos,” the network said in a statement.

“In terms of audience concentration, our schedule features television’s most affluent drama (‘West Wing’), situation comedy (‘Will & Grace’) and unscripted series (‘Apprentice’),” the Peacock Network said in a statement. “Further, our index increased year to year in both the A18-49 and A25-54 upscale income categories,” the network said. “Advertisers are attracted to this upscale concentration, which we continue to deliver.”

But Mike Shaw, president of sales for the ABC Television Network said, “You don’t get paid on indexing. You get paid on the rating that you deliver in the demographic.”

So while “The Apprentice” indexes higher than ABC’s “Desperate Housewives,” “Housewives” delivers more than twice the upscale viewers and commands about twice the price in the marketplace, he said.

On the other hand, advertisers might be able to pick up upscale viewers cheaper in a show with lower ratings overall but a high index, such as “The Office,” Mr. Sternberg said. NBC’s new comedy “My Name Is Earl,” despite its trailer-park setting, indexes high with upscale viewers.

Magna Global’s Mr. Sternberg prefers to measure upscale viewers based on a comparison with the population, rather than by the traditional indexing, which looks at the proportion of viewers watching a particular show or network. By his index, Mr. Sternberg said, ABC and NBC are tied.

He said the most upscale-indexing show among viewers 25 to 54 is “The Apprentice,” with a 205 index, followed by “Desperate Housewives,” “ER,” “Grey’s Anatomy” and “The Office.” “The West Wing” was ranked ninth, after “Earl.”

“Obviously, we’d rather be in the more upscale show for products that are at a higher price point, and we’re trying to reach an upscale audience,” said Andy Donchin, director of broadcast at Carat USA. “It’s something we throw in the mix. The bottom line is if you’re on a show that’s doing well, that’s attracting pretty big ratings, you’re probably reaching a lot of upscale viewers.”

ABC began its uptick among upscale viewers last season, but Ms. Wang said upscale growth is pacing ahead of the network’s growth in viewers overall.

CBS and Fox are behind ABC and NBC among upscale viewers. CBS’s average rating so far this season among those viewers is a 3.7, down from 4.0 last season. Its index is 94, down from 100 last season. Fox’s average rating is a 1.5, down from 2.3. Its index is 85, up from 65 a year ago.