What: Shares of Outerwall (NASDAQ:OUTR) have plunged today, down by 16% as of 12:49 p.m. ET, after the company reported fourth-quarter earnings showing a slowdown in its core Redbox business.

So what: Total revenue in the fourth quarter fell 12% to $527.2 million, which translated into adjusted earnings per share from continuing operations of $1.43, which topped analyst expectations. But guidance for 2016 fell flat by a large margin. Outerwall expects adjusted earnings per share to be in the range of $5 to $6.30 for 2016, while the Street had been modeling for $7.14 per share. Capital expenditures should be $45 million to $55 million.

Now what: Looking at Outerwall's different branded segments, the all-important Redbox video rental kiosks took a big hit. Redbox revenue in the fourth quarter fell 17% to $407 million, due to a 24% decrease in movie rental volumes. The kiosks rented out 135.8 million rentals during the fourth quarter, down from 179.5 million. The company noted the ongoing secular decline of physical video rentals, which appears to be accelerating in favor of digital platforms. A recent price increase also hurt demand among price-sensitive customers. Redbox still comprises 77% of the business, so any weakness there is going to be rather painful.