Wondering why Coca Cola is still running ads, even though everyone already knows what it is?
"The average observed change in brand sales was –16 percent after one year without advertising, dropping to –25 percent after two years, and reaching –36 percent after three years."
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"Larger, growing brands often were observed to continue to grow after advertising stopped, but almost all smaller, growing brands immediately began to decline." (not really coke's case, but still interesting)
Quotes from an article by Nicole Hartnett, Adam Gelzinis, Virginia Beal, Rachel Kennedy, and Byron Sharp.
"When Brands Go Dark. Examining Sales Trends when Brands Stop Broad-Reach Advertising for Long Periods"
http://www.journalofadvertisingresearch.com/content/61/3/247