NEW YORK: Despite a strong showing over the summer, overall TV adspend in the US declined -5.8% year-on-year in September and broadcast TV witnessed a particularly steep fall of -13.2%, a new industry report has revealed.

According to data from Standard Media Index (SMI), the sharp decline in broadcast TV adspend in September was largely because DraftKings and FanDuel, the fantasy football companies, spent $100m less last month than in September 2015.

Standard Media Index, which tracks 70% of US adspend from global and independent agencies, also reported that primetime revenue fell -16% compared to the same period last year.

Excluding sports, the average unit cost for the four major broadcast networks during primetime was $86,000, down -7.6% from $93,300 in 2015.

SMI added that many advertisers appear to have held back their upfront spend in September after committing a large amount of their budgets to the Summer Olympics. Consequently, upfront spend decreased -25% while scatter spend was up 32% year-on-year.

Looking at the broadcasters who gained in terms of revenue, SMI found NBC scored on Monday and Tuesday because of the success of The Voice and This is Us.

Fox and ABC tied for ad revenue on Wednesday, with Fox benefitting from its hit show Empire and ABC gaining from its comedy programming.

ABC also benefitted from sports on Thursday nights, although CBS won most overall revenue thanks to its Thursday Night Football.

Meanwhile, NBC emerged as the ad revenue winner on Sunday because of its football broadcasting, although ABC dominated Sunday nights among scripted programming.

Looking at cable, SMI said ESPN remained the highest grossing cable network by volume, but it saw an overall revenue decline of -10% year-on-year and a -4.5% fall in the price of its average 30-second spot.

And the presidential election boosted the three major 24-hour news networks, which all recorded double-digit revenue increases. Fox News saw revenues grow 16%, while CNN increased 25% and MSNBC jumped 28%.

"While some of September's falls can be attributed to a post Olympics hangover, evidence shows the biggest contributor to broadcast's significant fall was driven by the fantasy leagues spend almost completely drying up under the numerous legal actions they face," said James Fennessy, CEO of SMI.

"Cable's gains are directly related to the terrific results delivered by the news networks, which we fully expect to continue through the November election cycle," he added.

Data sourced from Standard Media Index; additional content by Warc staff