Ad spending was estimated at growing around 14% per year. In current times it's settled around 5-10% per year, but of course keep in mind that that's a compounding value. So a doubling isn't every 10-20 years but every ~7-14. And furthermore in their study they were able to demonstrate that shifts in happiness followed even local shifts in advertising. So when advertisers scaled back for various reasons, life satisfaction increased, and then began diminishing as the advertising returned.
Mass advertising will likely be the tobacco of our time once you consider the knock-on effects of societies full of individuals being made intentionally discontented.
[1] - https://www.zenithmedia.com/wp-content/uploads/2013/12/Adspe...