In April, a month or so after brands were accused of funding terrorist videos on YouTube, Procter & Gamble cut down the number of sites its ads ran on by 69.7%.
P&G froze YouTube spend but has since returned to YouTube's preferred channels.
However, even before the scandal broke, P&G's global chief brand officer Mark Pritchard had been urging the industry to band together to demand media transparency.
MediaRadar's ad tracking software has found that since that plunge, P&G has been gradually building up the number of sites it runs its ads on.
In May the number of sites was down 38% year-on-year, and by June only by 7%. In July, the sites were back on growth at 14% and in August they were up by 21%.
Nevertheless, for the months between January and August, P&G has run its ads on 20% fewer sites overall (1,251 sites), compared with the same period last year,
"The YouTube situation seemed to have startled P&G," Todd Krizelman, chief executive and co-founder of MediaRadar, said. "They ended up reducing the number of sites that they were running ads on – not just with YouTube, but in general. The numbers have bounced back dramatically since then, but the data suggests YouTube had a chilling effect."
He explained: "P&G has gained more transparency over its campaigns, which has resulted in a bounceback.
"They’re the biggest advertiser in the US and one of the biggest in the world. If they want more transparency, agencies, vendors and publishers are going to deliver it. Because of this, media partners have been compelled to install more brand safety measures in an effort to retain and win new business from P&G."
Only 922 sites of the 1,565 sites P&G advertised on survived the cull, a reduction of 69.7% and a carryover rate of only 59%.
"In the eyes of advertisers, transparency is more important than ever before," Krizelman added. "Brands are demanding increased transparency from their partners and cutting ties with those who don’t meet their strict standards. Our data shows that advertisers have become much more cautious with their campaigns, as many have reduced the number of sites they buy on."