What happened

Comcast (CMCSA -0.36%) saw its stock price fall in 2018 despite putting up relatively strong numbers. That probably happened because of fears that cord cutting would eventually cause problems in the company's core cable business.

The company has lost about 340,000 cable customers through three quarters. That's up from a drop of 151,000 in all of 2017. Customers are dropping cable in favor of streaming services in faster numbers, but Comcast has more than made up for those losses by adding broadband customers.

It's possible that the market for broadband reaches a saturation point, but that hasn't happened yet, and cable companies have been winning share from telephone-based providers. Comcast has added just over 1 million broadband customers through three quarters, around triple the number of cable customers it lost.

Two women sit on the floor of a living room, while one points to a large TV screen.

More consumers are dropping cable, putting a drag on Comcast shares. Image source: Getty Images.

So what

Fears over the decline of cable also cast a shadow over Comcast's broadcast and cable business. It's not that anything truly bad has happened yet. There's simply a fear that it will. That dragged the company's share price from $39.01 on the last day of trading in 2017 to $34.16 when the market closed for 2018, a 12% drop, according to data from S&P Global Market Intelligence.

CEO Brian Roberts doesn't share the market's concerns. In fact, he noted in his remarks in the third-quarter earnings release that the company grew in a number of ways in Q3.

"Comcast Cable's EBITDA growth was the fastest in six years, and customer relationship growth accelerated, driven by the best broadband net additions for a third quarter in 10 years," he said. "At NBCUniversal, our TV businesses continued their strong performance. NBC finished the 52-week season ranked No. 1 in total viewers for the first time in 16 years and No. 1 in adults 18-49 for the fifth consecutive season, and is off to a great start in the new season."

Now what

Roberts and Comcast have to show that the company can maintain its audience as customers drop traditional cable. That's a big challenge, because the company doesn't offer a streaming service, though it could do so in the future. That's a challenge, but one the company should be able to meet, given its strong lineup of intellectual property and its ability to market to its broadband customers.

Check out the latest Comcast earnings call transcript.