Nike Inc. has sold out 61 percent more merchandise since the controversial ad campaign featuring former NFL player Colin Kaepernick appeared earlier this month, according to data on the company's online sales from Thomson Reuters Proprietary Research.

Kaepernick, who sparked a national controversy by kneeling during the national anthem, first tweeted the ad on the Labor Day weekend, which immediately sparked demands for a boycott of the company's products.

President Donald Trump also tweeted, without providing evidence, that "Nike is getting absolutely killed with anger and boycotts."

But the research by Thomson Reuters, conducted in collaboration with StyleSage Co., showed the world's largest sportswear maker sold out far more items between Sept. 3 and Sept. 13 than in the 10-day period before the ad came out.

Nike discounted fewer products in the 10-day period after the ad and saw its Colin Kaepernick women's jersey sell out on Sept. 17, the research also showed.

"These strong statistics reinforce the notion that Nike is standing firm – and not just in a social context," said Jharonne Martis, director of consumer research at Thomson Reuters.

"They don't need to participate in the discounting that tends to plague other retail brands."

Thomson Reuters is the parent company of Reuters News.

Shares in Nike (NKE) have rebounded from an initial drop when the first versions of the ad were released, hitting a record high a little over a week later.

The stock is now up nearly 7 percent since the drop, outperforming a 1.9 percent gain for the Dow over the same period, helped by at least four analysts raising price targets ahead of first-quarter results on Sept. 25.

Social media sentiment around the company, which dived in the immediate aftermath of the ad, also turned positive earlier this week, according to Thomson Reuters' Eikon Social Media Monitor.

"(Nike's) new "Just Do It" ad campaign with Colin Kaepernick was a stroke of genius ... this premeditated move was another subtle but significant sign of Nike's strength and confidence in its position in the marketplace," Canaccord Genuity analyst Camilo Lyon wrote in a client note last week.