Discovery Communications (DISCA) - Get Report CEO David Zaslav on Tuesday acknowledged what media industry observers have been worried about for weeks: cord-cutting is increasing.

Zaslav, in an investor conference call, said Discovery was experiencing a "slight acceleration" in pay-TV subscriber declines. He put the figure at an annualized rate of 3%. And that is reason for worry.

According to a MoffettNathanson report made public a week ago, cord-cutting in the first quarter accelerated at the fastest pace ever. The media research firm put the annualized rate for pay-TV operators at 2.4%. Discovery, therefore, appears to be doing worst than the industry average.

With fewer subscribers, Discovery is experiencing slower revenue growth from pay-TV operators. During the quarter, affiliate fees increased 4.6%, compared with 5.6% in the fourth quarter of 2016 and 6.7% in the third quarter. Adding to concerns, Discovery has yet to win placement on any of the new online pay-TV platforms such as AT&T's (T) - Get Report DirecTV Now, Alphabet's (GOOGL) - Get Report YouTube TV or Hulu's newly launched multichannel streaming service.

As might be expected, Discovery's shares had tumbled nearly 4% to $26.17 on Tuesday morning, extending the stock's 2017 decline to 4.5%. By comparison, the benchmark S&P 500 index has gained 7.3% this year.

Discovery revenue for the first quarter fell short of analyst expectations: $1.61 billion compared with an average estimate of $1.63 billion. And while operating income before some costs did beat expectations -- $603 million compared with $598.3 million -- Zaslav noted that higher advertising rates helped to offset declining ratings for some networks, bolstering operations.

Adding to Discovery's woes, international advertising is showing signs of weakness. Discovery has made a big bet on owning European sports broadcaster Eurosport. Zaslav has made international expansion a cornerstone of the company's growth strategy. For Discovery, looking beyond a highly competitive U.S. market for faster growth abroad made sense.

But in an ominous sign for a company experiencing cable TV subscriber declines at home, Discovery's international advertising sales in the first quarter rose a mere 3%. And that 3%, AllianceBernstein's Todd Juenger pointed out, largely was due to a comparison with the previous quarter when a carriage-fee disagreement with Norway's Telenor resulted in a money-losing blackout for both sides.

In recent years, Discovery posted increases in international ad sales that reached the double-digit percentiles. Growth often hit the high-teens or even surpassed 20%. Those days seem to be over.

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