In 2018, Irish whiskey sales in the U.S. topped $1 billion for the first time in history. Mixed martial arts (MMA) fighter Connor McGregor was quick to take credit for the record-breaking figure, writing on Twitter: “Was there ever any doubt I’d turn Whiskey to a Billi?”

McGregor launched his Proper No. Twelve Irish whiskey in September 2018. The brand hit its six-month sales target in just 10 days, but inspection of the 2018 sales data shows McGregor’s claims are heavily inflated: Proper No. Twelve accounted for just 4 percent of Irish whiskey sales in the U.S.

One thing McGregor might be able to take credit for, however, is inflicting a sales slump on the category’s leading brand.

Jameson is the world’s top-selling Irish whiskey and also leads sales in the U.S. In 2018, the brand saw a 12 percent sales increase compared to 2017, but Jameson’s growth is also slowing. Some analysts attribute this to the success of new Irish whiskey brands, including Proper No. Twelve.

Speaking to the Irish Times, Edward Mundy, a market analyst for Jefferies, described this as “natural slowdown” but also said new brands — most notably Proper No. Twelve — have likely played a part.

“The informal ambition is for Pernod Ricard in the US to grow ahead of the market,” Mundy says. “If Jameson is disrupted by Proper No. Twelve, this makes this ambition harder to achieve in the near term.”

But McGregor’s Proper No. Twelve Irish whiskey still has a long way to go before it starts to look anything like a rival for Jameson. To date, his brand has shipped around 200,000 nine-liter cases, compared to the 7.3 million nine-liter cases Jameson sold in the 12 months ending June 2018.