The K-pop music industry has extended its growth momentum this year with a surge in physical album sales in January, according to data compiled by South Korean music chart tracker Gaon Chart.

The top 400 albums sold more than 4.05 million copies in and out of the country last month, up 66.9 percent from the same period previous year. The figure, however, dropped by 5.4 percentage points from December, the data showed.

Of the top 400 albums, boy band Enhypen topped the list by selling 723,478 copies of “Dimension: Answer,” a repackaging of the act’s million-selling first studio album “Dimension: Dilemma,” which was released on Jan. 10.

It was followed by S.M. Entertainment’s winter special album “2021 Winter SMTOWN: SMCU Express” and girl group Kep1er’s debut album “First Impact,” with the sales volume of 347,434 copies and 300,099 copies, respectively.

Gaon Chart’s head researcher Kim Jin-woo said the sharp increase was a “very positive outcome,” as January in general is a relatively slow month. The increase was largely attributable to the rapidly growing K-pop physical album market, he explained.

In the meantime, digital music sales in the same month remained almost unchanged from a year earlier.

January’s accumulated sales of the top 400 songs saw a slight on-year increase, up by 0.4 percent from a year prior. But compared to the previous month, it represented a 7.1 percent on-month drop.

MeloMance’s Kim Min-seok’s “DrunKen Confession” secured the No.1 spot on the list, followed by rapper Sokodomo’s “MERRY-GO-ROUND (Feat. Zion.T & Wonstein)” and rapper-songwriter Be’O’s “Counting Stars.”

“Digital music sales in the first half this year are likely to show a similar pattern as last year,” Kim said. “If the possibility of COVID-19 becoming endemic in the latter half increases, the market will likely rebound once or twice.”